Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
Hi Am 14.04.23 um 09:56 schrieb Daniel Vetter: On Fri, 14 Apr 2023 at 09:34, Thomas Zimmermann wrote: [...] There's also no need/way to change video modes or formats in the shadow buffer. If we'd ever support that, it would be implemented in the DRM driver's modesetting. The relationship between GEM buffer and shadow buffer remains unaffected by this. Try it and be amazed :-) It's not supported. I don't know if we catch all the cases, but at least we try. And I don't think we will ever support changes to the video mode. The framebuffer width/height binds us to certain constrains during the damage handling. Figuring all this out is probably not worth the effort. I've seen enough syzkaller bugs and screamed at them that yes we do this. Also xres/yres is the wrong thing even if you don't use fb ioctl to change things up in multi-monitor cases (we allocate the drm_fb/fbdev virtual size to match the biggest resolution, but then set fbinfo->var.x/yres to match the smallest to make sure fbcon is fully visible everywhere). I think you're confusion is the perfect case for why we really should use fb->height/width/pitches[0] here. I really don't see the point of building a DRM-only variant when there's the same code in fbdev drivers. Required information is all stored in the fb_info. The helper code should be seen as part of fbdev's deferred I/O. This, however, is independent from the limitation where the memory size has to be a multiple of the framebuffer resolution. That's a limitation imposed by DRM. Please also note that this is only relevant for fbdev-generic. I intent to move some of those damage helpers there. I'd assume that will make the whole thing a bit more understandable. (Unfortunately, the fbdev emulation has been a victim of false starts and complexity. It takes time to fix all this.) I'm not sure why you refer to xres/yres; I think, the smem_length and line_length is what we'd need in most cases. Best regards Thomas -Daniel Best regards Thomas The xres_virtual/yres_virtual should always match drm_fb sizes (but we've had bugs in the past for that, only recently fixed all in linux-next), because that's supposed to be the max size. And since we never reallocate the fbdev emulation fb (at least with the current code) this should never change. But fundamentally you're bringing up a very good point, we've had piles of bugs in the past with not properly validating the fbdev side information in info->var, and a bunch of resulting bugs. So validating against the drm side of things should be a bit more robust. It's kinda the same we do for legacy kms ioctls: We translate that to atomic kms as fast as possible, and then do the entire subsequent validation with atomic kms data structures. -Daniel The thing is, if you change this further to just pass the drm_framebuffer, then this 100% becomes a drm function, which could be used by anything in drm really. I agree with you. If I use fb_width/fb_height directly and bypassing 'info->var.xres" and "info->var.yres", the code style diverged then. As far as I am understanding, the clip happen on the front end, the actual damage update happen at back end. Using the data structure come with the front end is more reasonable for current implement. But also *shrug*. I can convert this single function to 100% drm with another patch. But, maybe there also have other functions are not 100% drm I would like do something to help achieve this in the future, let me help to fix this bug first? -Daniel -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Maxfeldstr. 5, 90409 Nürnberg, Germany (HRB 36809, AG Nürnberg) Geschäftsführer: Ivo Totev OpenPGP_signature Description: OpenPGP digital signature
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
On Fri, Apr 14, 2023 at 07:30:53PM +0800, Sui Jingfeng wrote:
> Hi,
>
> On 2023/4/14 15:56, Daniel Vetter wrote:
> > On Fri, 14 Apr 2023 at 09:34, Thomas Zimmermann wrote:
> > > Hi
> > >
> > > Am 14.04.23 um 07:36 schrieb Daniel Vetter:
> > > > On Fri, 14 Apr 2023 at 06:24, Sui Jingfeng <15330273...@189.cn> wrote:
> > > > > Hi,
> > > > >
> > > > > On 2023/4/14 04:01, Daniel Vetter wrote:
> > > > > > On Thu, Apr 13, 2023 at 09:20:23PM +0200, Thomas Zimmermann wrote:
> > > > > > > Hi
> > > > > > >
> > > > > > > Am 13.04.23 um 20:56 schrieb Daniel Vetter:
> > > > > > > [...]
> > > > > > > > This should switch the existing code over to using
> > > > > > > > drm_framebuffer instead
> > > > > > > > of fbdev:
> > > > > > > >
> > > > > > > >
> > > > > > > > diff --git a/drivers/gpu/drm/drm_fb_helper.c
> > > > > > > > b/drivers/gpu/drm/drm_fb_helper.c
> > > > > > > > index ef4eb8b12766..99ca69dd432f 100644
> > > > > > > > --- a/drivers/gpu/drm/drm_fb_helper.c
> > > > > > > > +++ b/drivers/gpu/drm/drm_fb_helper.c
> > > > > > > > @@ -647,22 +647,26 @@ static void drm_fb_helper_damage(struct
> > > > > > > > drm_fb_helper *helper, u32 x, u32 y,
> > > > > > > > static void drm_fb_helper_memory_range_to_clip(struct
> > > > > > > > fb_info *info, off_t off, size_t len,
> > > > > > > > struct drm_rect
> > > > > > > > *clip)
> > > > > > > > {
> > > > > > > > + struct drm_fb_helper *helper = info->par;
> > > > > > > > +
> > > > > > > > off_t end = off + len;
> > > > > > > > u32 x1 = 0;
> > > > > > > > u32 y1 = off / info->fix.line_length;
> > > > > > > > - u32 x2 = info->var.xres;
> > > > > > > > - u32 y2 = DIV_ROUND_UP(end, info->fix.line_length);
> > > > > > > > + u32 x2 = helper->fb->height;
> > > > > > > > + unsigned stride = helper->fb->pitches[0];
> > > > > > > > + u32 y2 = DIV_ROUND_UP(end, stride);
> > > > > > > > + int bpp = drm_format_info_bpp(helper->fb->format, 0);
> > > > > > > Please DONT do that. The code here is fbdev code and shouldn't
> > > > > > > bother about
> > > > > > > DRM data structures. Actually, it shouldn't be here: a number of
> > > > > > > fbdev
> > > > > > > drivers with deferred I/O contain similar code and the fbdev
> > > > > > > module should
> > > > > > > provide us with a helper. (I think I even had some patches
> > > > > > > somewhere.)
> > > > > > Well my thinking is that it's a drm driver,
> > > > > Yes, I actually agree with this, and the code looks quite good. And I
> > > > > really want to adopt it.
> > > > >
> > > > > Because here is DRM, we should emulate the fbdev in the DRM's way.
> > > > >
> > > > > The DRM is really the big brother on the behind of emulated fbdev,
> > > > >
> > > > > who provide the real displayable backing memory and scant out engine
> > > > > to
> > > > > display such a buffer.
> > > > >
> > > > >
> > > > > But currently, the fact is, drm_fb_helper.c still initializes lots of
> > > > > data structure come from fbdev world.
> > > > >
> > > > > For example, the drm_fb_helper_fill_fix() and drm_fb_helper_fill_var()
> > > > > in drm_fb_helper_fill_info() function.
> > > > >
> > > > > This saying implicitly that the fbdev-generic is a glue layer which
> > > > > copy
> > > > > damage frame buffer data
> > > > >
> > > > > from the front end(fbdev layer) to its drm backend. It's not a 100%
> > > > > replacement its fbdev front end,
> > > > >
> > > > > rather, it relay on it.
> > > > >
> > > > >
> > > > > > so if we have issue with limit
> > > > > > checks blowing up it makes more sense to check them against drm
> > > > > > limits.
> > > > > > Plus a lot more people understand those than fbdev. They should all
> > > > > > match
> > > > > > anyway, or if they dont, we have a bug.
> > > > > Yes, this is really what I'm worry about.
> > > > >
> > > > > I see that members of struct fb_var_screeninfo can be changed by
> > > > > user-space. For example, xoffset and yoffset.
> > > > >
> > > > > There is no change about 'info->var.xres' and 'info->var.yres' from
> > > > > the
> > > > > userspace,
> > > > >
> > > > > therefore, they should all match in practice.
> > > > >
> > > > >
> > > > > User-space can choose a use a smaller dispaly area than 'var.xres x
> > > > > var.yres',
> > > > >
> > > > > but that is implemented with 'var.xoffset' and 'var.xoffset'.
> > > > >
> > > > > But consider that the name 'var', which may stand for 'variation' or
> > > > > 'vary'. This is terrifying.
> > > > >
> > > > > I imagine, with a shadow buffer, the front end can do any modeset on
> > > > > the
> > > > > runtime freely,
> > > > >
> > > > > including change the format of frame buffer on the runtime. Just do
> > > > > not
> > > > > out-of-bound.
> > > > >
> > > > > The middle do the conversion on the fly.
> > > > >
> > > > >
> > > > > We might also create double shadow buffer size to allow the front end
> > > > > to
> > > > > pan?
> > > > Yeah so the
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
Hi,
On 2023/4/14 15:56, Daniel Vetter wrote:
On Fri, 14 Apr 2023 at 09:34, Thomas Zimmermann wrote:
Hi
Am 14.04.23 um 07:36 schrieb Daniel Vetter:
On Fri, 14 Apr 2023 at 06:24, Sui Jingfeng <15330273...@189.cn> wrote:
Hi,
On 2023/4/14 04:01, Daniel Vetter wrote:
On Thu, Apr 13, 2023 at 09:20:23PM +0200, Thomas Zimmermann wrote:
Hi
Am 13.04.23 um 20:56 schrieb Daniel Vetter:
[...]
This should switch the existing code over to using drm_framebuffer instead
of fbdev:
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index ef4eb8b12766..99ca69dd432f 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -647,22 +647,26 @@ static void drm_fb_helper_damage(struct drm_fb_helper
*helper, u32 x, u32 y,
static void drm_fb_helper_memory_range_to_clip(struct fb_info *info, off_t
off, size_t len,
struct drm_rect *clip)
{
+ struct drm_fb_helper *helper = info->par;
+
off_t end = off + len;
u32 x1 = 0;
u32 y1 = off / info->fix.line_length;
- u32 x2 = info->var.xres;
- u32 y2 = DIV_ROUND_UP(end, info->fix.line_length);
+ u32 x2 = helper->fb->height;
+ unsigned stride = helper->fb->pitches[0];
+ u32 y2 = DIV_ROUND_UP(end, stride);
+ int bpp = drm_format_info_bpp(helper->fb->format, 0);
Please DONT do that. The code here is fbdev code and shouldn't bother about
DRM data structures. Actually, it shouldn't be here: a number of fbdev
drivers with deferred I/O contain similar code and the fbdev module should
provide us with a helper. (I think I even had some patches somewhere.)
Well my thinking is that it's a drm driver,
Yes, I actually agree with this, and the code looks quite good. And I
really want to adopt it.
Because here is DRM, we should emulate the fbdev in the DRM's way.
The DRM is really the big brother on the behind of emulated fbdev,
who provide the real displayable backing memory and scant out engine to
display such a buffer.
But currently, the fact is, drm_fb_helper.c still initializes lots of
data structure come from fbdev world.
For example, the drm_fb_helper_fill_fix() and drm_fb_helper_fill_var()
in drm_fb_helper_fill_info() function.
This saying implicitly that the fbdev-generic is a glue layer which copy
damage frame buffer data
from the front end(fbdev layer) to its drm backend. It's not a 100%
replacement its fbdev front end,
rather, it relay on it.
so if we have issue with limit
checks blowing up it makes more sense to check them against drm limits.
Plus a lot more people understand those than fbdev. They should all match
anyway, or if they dont, we have a bug.
Yes, this is really what I'm worry about.
I see that members of struct fb_var_screeninfo can be changed by
user-space. For example, xoffset and yoffset.
There is no change about 'info->var.xres' and 'info->var.yres' from the
userspace,
therefore, they should all match in practice.
User-space can choose a use a smaller dispaly area than 'var.xres x
var.yres',
but that is implemented with 'var.xoffset' and 'var.xoffset'.
But consider that the name 'var', which may stand for 'variation' or
'vary'. This is terrifying.
I imagine, with a shadow buffer, the front end can do any modeset on the
runtime freely,
including change the format of frame buffer on the runtime. Just do not
out-of-bound.
The middle do the conversion on the fly.
We might also create double shadow buffer size to allow the front end to
pan?
Yeah so the front should be able to pan. And the front-end can
actually make xres/yres smalle than drm_fb->height/width, so we _have_
to use the fb side of things. Otherwise it's a bug I just realized.
What are you talking about? The GEM buffer is a full fbdev framebuffer,
which is screen resolution multiplied by the overall factor. The shadow
buffer is exactly the same size. You can already easily pan within these
buffers.
There's also no need/way to change video modes or formats in the shadow
buffer. If we'd ever support that, it would be implemented in the DRM
driver's modesetting. The relationship between GEM buffer and shadow
buffer remains unaffected by this.
Try it and be amazed :-) I've seen enough syzkaller bugs and screamed
at them that yes we do this. Also xres/yres is the wrong thing even if
you don't use fb ioctl to change things up in multi-monitor cases (we
allocate the drm_fb/fbdev virtual size to match the biggest
resolution, but then set fbinfo->var.x/yres to match the smallest to
make sure fbcon is fully visible everywhere).
I think you're confusion is the perfect case for why we really should
use fb->height/width/pitches[0] here.
-Daniel
Exactly,
This what I'm worry about, if someone add code with changing xres/yres
from userspace
via fb ioctl implemented. Then, xres/yres and
fb->height/width/pitches[0] may not match.
so fetch data from fbinfo->var.x/yres still more safe.
Yet, on our platform with drm/loongson driver
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
On Fri, 14 Apr 2023 at 09:34, Thomas Zimmermann wrote:
>
> Hi
>
> Am 14.04.23 um 07:36 schrieb Daniel Vetter:
> > On Fri, 14 Apr 2023 at 06:24, Sui Jingfeng <15330273...@189.cn> wrote:
> >>
> >> Hi,
> >>
> >> On 2023/4/14 04:01, Daniel Vetter wrote:
> >>> On Thu, Apr 13, 2023 at 09:20:23PM +0200, Thomas Zimmermann wrote:
> Hi
>
> Am 13.04.23 um 20:56 schrieb Daniel Vetter:
> [...]
> > This should switch the existing code over to using drm_framebuffer
> > instead
> > of fbdev:
> >
> >
> > diff --git a/drivers/gpu/drm/drm_fb_helper.c
> > b/drivers/gpu/drm/drm_fb_helper.c
> > index ef4eb8b12766..99ca69dd432f 100644
> > --- a/drivers/gpu/drm/drm_fb_helper.c
> > +++ b/drivers/gpu/drm/drm_fb_helper.c
> > @@ -647,22 +647,26 @@ static void drm_fb_helper_damage(struct
> > drm_fb_helper *helper, u32 x, u32 y,
> > static void drm_fb_helper_memory_range_to_clip(struct fb_info
> > *info, off_t off, size_t len,
> > struct drm_rect *clip)
> > {
> > + struct drm_fb_helper *helper = info->par;
> > +
> > off_t end = off + len;
> > u32 x1 = 0;
> > u32 y1 = off / info->fix.line_length;
> > - u32 x2 = info->var.xres;
> > - u32 y2 = DIV_ROUND_UP(end, info->fix.line_length);
> > + u32 x2 = helper->fb->height;
> > + unsigned stride = helper->fb->pitches[0];
> > + u32 y2 = DIV_ROUND_UP(end, stride);
> > + int bpp = drm_format_info_bpp(helper->fb->format, 0);
> Please DONT do that. The code here is fbdev code and shouldn't bother
> about
> DRM data structures. Actually, it shouldn't be here: a number of fbdev
> drivers with deferred I/O contain similar code and the fbdev module
> should
> provide us with a helper. (I think I even had some patches somewhere.)
> >>> Well my thinking is that it's a drm driver,
> >>
> >> Yes, I actually agree with this, and the code looks quite good. And I
> >> really want to adopt it.
> >>
> >> Because here is DRM, we should emulate the fbdev in the DRM's way.
> >>
> >> The DRM is really the big brother on the behind of emulated fbdev,
> >>
> >> who provide the real displayable backing memory and scant out engine to
> >> display such a buffer.
> >>
> >>
> >> But currently, the fact is, drm_fb_helper.c still initializes lots of
> >> data structure come from fbdev world.
> >>
> >> For example, the drm_fb_helper_fill_fix() and drm_fb_helper_fill_var()
> >> in drm_fb_helper_fill_info() function.
> >>
> >> This saying implicitly that the fbdev-generic is a glue layer which copy
> >> damage frame buffer data
> >>
> >> from the front end(fbdev layer) to its drm backend. It's not a 100%
> >> replacement its fbdev front end,
> >>
> >> rather, it relay on it.
> >>
> >>
> >>> so if we have issue with limit
> >>> checks blowing up it makes more sense to check them against drm limits.
> >>> Plus a lot more people understand those than fbdev. They should all match
> >>> anyway, or if they dont, we have a bug.
> >>
> >> Yes, this is really what I'm worry about.
> >>
> >> I see that members of struct fb_var_screeninfo can be changed by
> >> user-space. For example, xoffset and yoffset.
> >>
> >> There is no change about 'info->var.xres' and 'info->var.yres' from the
> >> userspace,
> >>
> >> therefore, they should all match in practice.
> >>
> >>
> >> User-space can choose a use a smaller dispaly area than 'var.xres x
> >> var.yres',
> >>
> >> but that is implemented with 'var.xoffset' and 'var.xoffset'.
> >>
> >> But consider that the name 'var', which may stand for 'variation' or
> >> 'vary'. This is terrifying.
> >>
> >> I imagine, with a shadow buffer, the front end can do any modeset on the
> >> runtime freely,
> >>
> >> including change the format of frame buffer on the runtime. Just do not
> >> out-of-bound.
> >>
> >> The middle do the conversion on the fly.
> >>
> >>
> >> We might also create double shadow buffer size to allow the front end to
> >> pan?
> >
> > Yeah so the front should be able to pan. And the front-end can
> > actually make xres/yres smalle than drm_fb->height/width, so we _have_
> > to use the fb side of things. Otherwise it's a bug I just realized.
>
> What are you talking about? The GEM buffer is a full fbdev framebuffer,
> which is screen resolution multiplied by the overall factor. The shadow
> buffer is exactly the same size. You can already easily pan within these
> buffers.
>
> There's also no need/way to change video modes or formats in the shadow
> buffer. If we'd ever support that, it would be implemented in the DRM
> driver's modesetting. The relationship between GEM buffer and shadow
> buffer remains unaffected by this.
Try it and be amazed :-) I've seen enough syzkaller bugs and screamed
at them that yes we do this. Also xres/yres is the wrong thing even if
you don't use fb ioctl to change things up in multi-monitor cases (we
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
Am 14.04.23 um 09:34 schrieb Thomas Zimmermann:
Hi
Am 14.04.23 um 07:36 schrieb Daniel Vetter:
On Fri, 14 Apr 2023 at 06:24, Sui Jingfeng <15330273...@189.cn> wrote:
Hi,
On 2023/4/14 04:01, Daniel Vetter wrote:
On Thu, Apr 13, 2023 at 09:20:23PM +0200, Thomas Zimmermann wrote:
Hi
Am 13.04.23 um 20:56 schrieb Daniel Vetter:
[...]
This should switch the existing code over to using drm_framebuffer
instead
of fbdev:
diff --git a/drivers/gpu/drm/drm_fb_helper.c
b/drivers/gpu/drm/drm_fb_helper.c
index ef4eb8b12766..99ca69dd432f 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -647,22 +647,26 @@ static void drm_fb_helper_damage(struct
drm_fb_helper *helper, u32 x, u32 y,
static void drm_fb_helper_memory_range_to_clip(struct fb_info
*info, off_t off, size_t len,
struct drm_rect *clip)
{
+ struct drm_fb_helper *helper = info->par;
+
off_t end = off + len;
u32 x1 = 0;
u32 y1 = off / info->fix.line_length;
- u32 x2 = info->var.xres;
- u32 y2 = DIV_ROUND_UP(end, info->fix.line_length);
+ u32 x2 = helper->fb->height;
+ unsigned stride = helper->fb->pitches[0];
+ u32 y2 = DIV_ROUND_UP(end, stride);
+ int bpp = drm_format_info_bpp(helper->fb->format, 0);
Please DONT do that. The code here is fbdev code and shouldn't
bother about
DRM data structures. Actually, it shouldn't be here: a number of fbdev
drivers with deferred I/O contain similar code and the fbdev module
should
provide us with a helper. (I think I even had some patches somewhere.)
Well my thinking is that it's a drm driver,
Yes, I actually agree with this, and the code looks quite good. And I
really want to adopt it.
Because here is DRM, we should emulate the fbdev in the DRM's way.
The DRM is really the big brother on the behind of emulated fbdev,
who provide the real displayable backing memory and scant out engine to
display such a buffer.
But currently, the fact is, drm_fb_helper.c still initializes lots of
data structure come from fbdev world.
For example, the drm_fb_helper_fill_fix() and drm_fb_helper_fill_var()
in drm_fb_helper_fill_info() function.
This saying implicitly that the fbdev-generic is a glue layer which copy
damage frame buffer data
from the front end(fbdev layer) to its drm backend. It's not a 100%
replacement its fbdev front end,
rather, it relay on it.
so if we have issue with limit
checks blowing up it makes more sense to check them against drm limits.
Plus a lot more people understand those than fbdev. They should all
match
anyway, or if they dont, we have a bug.
Yes, this is really what I'm worry about.
I see that members of struct fb_var_screeninfo can be changed by
user-space. For example, xoffset and yoffset.
There is no change about 'info->var.xres' and 'info->var.yres' from the
userspace,
therefore, they should all match in practice.
User-space can choose a use a smaller dispaly area than 'var.xres x
var.yres',
but that is implemented with 'var.xoffset' and 'var.xoffset'.
But consider that the name 'var', which may stand for 'variation' or
'vary'. This is terrifying.
I imagine, with a shadow buffer, the front end can do any modeset on the
runtime freely,
including change the format of frame buffer on the runtime. Just do not
out-of-bound.
The middle do the conversion on the fly.
We might also create double shadow buffer size to allow the front end to
pan?
Yeah so the front should be able to pan. And the front-end can
actually make xres/yres smalle than drm_fb->height/width, so we _have_
to use the fb side of things. Otherwise it's a bug I just realized.
What are you talking about? The GEM buffer is a full fbdev framebuffer,
which is screen resolution multiplied by the overall factor. The shadow
s/overall/overalloc'
buffer is exactly the same size. You can already easily pan within these
buffers.
There's also no need/way to change video modes or formats in the shadow
buffer. If we'd ever support that, it would be implemented in the DRM
driver's modesetting. The relationship between GEM buffer and shadow
buffer remains unaffected by this.
Best regards
Thomas
The xres_virtual/yres_virtual should always match drm_fb sizes (but
we've had bugs in the past for that, only recently fixed all in
linux-next), because that's supposed to be the max size. And since we
never reallocate the fbdev emulation fb (at least with the current
code) this should never change.
But fundamentally you're bringing up a very good point, we've had
piles of bugs in the past with not properly validating the fbdev side
information in info->var, and a bunch of resulting bugs. So validating
against the drm side of things should be a bit more robust.
It's kinda the same we do for legacy kms ioctls: We translate that to
atomic kms as fast as possible, and then do the entire subsequent
validation with atomic kms data structures.
-Daniel
The thing is, if you change
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
Hi
Am 14.04.23 um 07:36 schrieb Daniel Vetter:
On Fri, 14 Apr 2023 at 06:24, Sui Jingfeng <15330273...@189.cn> wrote:
Hi,
On 2023/4/14 04:01, Daniel Vetter wrote:
On Thu, Apr 13, 2023 at 09:20:23PM +0200, Thomas Zimmermann wrote:
Hi
Am 13.04.23 um 20:56 schrieb Daniel Vetter:
[...]
This should switch the existing code over to using drm_framebuffer instead
of fbdev:
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index ef4eb8b12766..99ca69dd432f 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -647,22 +647,26 @@ static void drm_fb_helper_damage(struct drm_fb_helper
*helper, u32 x, u32 y,
static void drm_fb_helper_memory_range_to_clip(struct fb_info *info, off_t
off, size_t len,
struct drm_rect *clip)
{
+ struct drm_fb_helper *helper = info->par;
+
off_t end = off + len;
u32 x1 = 0;
u32 y1 = off / info->fix.line_length;
- u32 x2 = info->var.xres;
- u32 y2 = DIV_ROUND_UP(end, info->fix.line_length);
+ u32 x2 = helper->fb->height;
+ unsigned stride = helper->fb->pitches[0];
+ u32 y2 = DIV_ROUND_UP(end, stride);
+ int bpp = drm_format_info_bpp(helper->fb->format, 0);
Please DONT do that. The code here is fbdev code and shouldn't bother about
DRM data structures. Actually, it shouldn't be here: a number of fbdev
drivers with deferred I/O contain similar code and the fbdev module should
provide us with a helper. (I think I even had some patches somewhere.)
Well my thinking is that it's a drm driver,
Yes, I actually agree with this, and the code looks quite good. And I
really want to adopt it.
Because here is DRM, we should emulate the fbdev in the DRM's way.
The DRM is really the big brother on the behind of emulated fbdev,
who provide the real displayable backing memory and scant out engine to
display such a buffer.
But currently, the fact is, drm_fb_helper.c still initializes lots of
data structure come from fbdev world.
For example, the drm_fb_helper_fill_fix() and drm_fb_helper_fill_var()
in drm_fb_helper_fill_info() function.
This saying implicitly that the fbdev-generic is a glue layer which copy
damage frame buffer data
from the front end(fbdev layer) to its drm backend. It's not a 100%
replacement its fbdev front end,
rather, it relay on it.
so if we have issue with limit
checks blowing up it makes more sense to check them against drm limits.
Plus a lot more people understand those than fbdev. They should all match
anyway, or if they dont, we have a bug.
Yes, this is really what I'm worry about.
I see that members of struct fb_var_screeninfo can be changed by
user-space. For example, xoffset and yoffset.
There is no change about 'info->var.xres' and 'info->var.yres' from the
userspace,
therefore, they should all match in practice.
User-space can choose a use a smaller dispaly area than 'var.xres x
var.yres',
but that is implemented with 'var.xoffset' and 'var.xoffset'.
But consider that the name 'var', which may stand for 'variation' or
'vary'. This is terrifying.
I imagine, with a shadow buffer, the front end can do any modeset on the
runtime freely,
including change the format of frame buffer on the runtime. Just do not
out-of-bound.
The middle do the conversion on the fly.
We might also create double shadow buffer size to allow the front end to
pan?
Yeah so the front should be able to pan. And the front-end can
actually make xres/yres smalle than drm_fb->height/width, so we _have_
to use the fb side of things. Otherwise it's a bug I just realized.
What are you talking about? The GEM buffer is a full fbdev framebuffer,
which is screen resolution multiplied by the overall factor. The shadow
buffer is exactly the same size. You can already easily pan within these
buffers.
There's also no need/way to change video modes or formats in the shadow
buffer. If we'd ever support that, it would be implemented in the DRM
driver's modesetting. The relationship between GEM buffer and shadow
buffer remains unaffected by this.
Best regards
Thomas
The xres_virtual/yres_virtual should always match drm_fb sizes (but
we've had bugs in the past for that, only recently fixed all in
linux-next), because that's supposed to be the max size. And since we
never reallocate the fbdev emulation fb (at least with the current
code) this should never change.
But fundamentally you're bringing up a very good point, we've had
piles of bugs in the past with not properly validating the fbdev side
information in info->var, and a bunch of resulting bugs. So validating
against the drm side of things should be a bit more robust.
It's kinda the same we do for legacy kms ioctls: We translate that to
atomic kms as fast as possible, and then do the entire subsequent
validation with atomic kms data structures.
-Daniel
The thing is, if you change this
further to just pass the drm_framebuffer, then this 100% becomes a drm
function,
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
Hi
Am 13.04.23 um 22:01 schrieb Daniel Vetter:
On Thu, Apr 13, 2023 at 09:20:23PM +0200, Thomas Zimmermann wrote:
Hi
Am 13.04.23 um 20:56 schrieb Daniel Vetter:
[...]
This should switch the existing code over to using drm_framebuffer instead
of fbdev:
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index ef4eb8b12766..99ca69dd432f 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -647,22 +647,26 @@ static void drm_fb_helper_damage(struct drm_fb_helper
*helper, u32 x, u32 y,
static void drm_fb_helper_memory_range_to_clip(struct fb_info *info, off_t
off, size_t len,
struct drm_rect *clip)
{
+ struct drm_fb_helper *helper = info->par;
+
off_t end = off + len;
u32 x1 = 0;
u32 y1 = off / info->fix.line_length;
- u32 x2 = info->var.xres;
- u32 y2 = DIV_ROUND_UP(end, info->fix.line_length);
+ u32 x2 = helper->fb->height;
+ unsigned stride = helper->fb->pitches[0];
+ u32 y2 = DIV_ROUND_UP(end, stride);
+ int bpp = drm_format_info_bpp(helper->fb->format, 0);
Please DONT do that. The code here is fbdev code and shouldn't bother about
DRM data structures. Actually, it shouldn't be here: a number of fbdev
drivers with deferred I/O contain similar code and the fbdev module should
provide us with a helper. (I think I even had some patches somewhere.)
Well my thinking is that it's a drm driver, so if we have issue with limit
Technically, it's not a driver, but a client.
checks blowing up it makes more sense to check them against drm limits.
You can still do this in fb_dirty during the actual update.
Plus a lot more people understand those than fbdev. They should all match
anyway, or if they dont, we have a bug. The thing is, if you change this
further to just pass the drm_framebuffer, then this 100% becomes a drm
function, which could be used by anything in drm really.
The code is only useful to fbdev-generic and a number older of fbdev
drivers. Nothing else uses deferred I/O and the rsp damage handling.
Anything else operates directly on memory buffers. (i915 is a bit
special, but doesn't use this damage handling.) The function really
should not be here.
I'd push back on additional DRM code with fbdev deferred I/O. Drivers'
fbdev should either operate directly on GEM buffers; or the driver
should employ fbdev-generic.
Best regards
Thomas
But also *shrug*.
-Daniel
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
OpenPGP_signature
Description: OpenPGP digital signature
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
On Fri, 14 Apr 2023 at 06:24, Sui Jingfeng <15330273...@189.cn> wrote:
>
> Hi,
>
> On 2023/4/14 04:01, Daniel Vetter wrote:
> > On Thu, Apr 13, 2023 at 09:20:23PM +0200, Thomas Zimmermann wrote:
> >> Hi
> >>
> >> Am 13.04.23 um 20:56 schrieb Daniel Vetter:
> >> [...]
> >>> This should switch the existing code over to using drm_framebuffer instead
> >>> of fbdev:
> >>>
> >>>
> >>> diff --git a/drivers/gpu/drm/drm_fb_helper.c
> >>> b/drivers/gpu/drm/drm_fb_helper.c
> >>> index ef4eb8b12766..99ca69dd432f 100644
> >>> --- a/drivers/gpu/drm/drm_fb_helper.c
> >>> +++ b/drivers/gpu/drm/drm_fb_helper.c
> >>> @@ -647,22 +647,26 @@ static void drm_fb_helper_damage(struct
> >>> drm_fb_helper *helper, u32 x, u32 y,
> >>>static void drm_fb_helper_memory_range_to_clip(struct fb_info *info,
> >>> off_t off, size_t len,
> >>>struct drm_rect *clip)
> >>>{
> >>> + struct drm_fb_helper *helper = info->par;
> >>> +
> >>> off_t end = off + len;
> >>> u32 x1 = 0;
> >>> u32 y1 = off / info->fix.line_length;
> >>> - u32 x2 = info->var.xres;
> >>> - u32 y2 = DIV_ROUND_UP(end, info->fix.line_length);
> >>> + u32 x2 = helper->fb->height;
> >>> + unsigned stride = helper->fb->pitches[0];
> >>> + u32 y2 = DIV_ROUND_UP(end, stride);
> >>> + int bpp = drm_format_info_bpp(helper->fb->format, 0);
> >> Please DONT do that. The code here is fbdev code and shouldn't bother about
> >> DRM data structures. Actually, it shouldn't be here: a number of fbdev
> >> drivers with deferred I/O contain similar code and the fbdev module should
> >> provide us with a helper. (I think I even had some patches somewhere.)
> > Well my thinking is that it's a drm driver,
>
> Yes, I actually agree with this, and the code looks quite good. And I
> really want to adopt it.
>
> Because here is DRM, we should emulate the fbdev in the DRM's way.
>
> The DRM is really the big brother on the behind of emulated fbdev,
>
> who provide the real displayable backing memory and scant out engine to
> display such a buffer.
>
>
> But currently, the fact is, drm_fb_helper.c still initializes lots of
> data structure come from fbdev world.
>
> For example, the drm_fb_helper_fill_fix() and drm_fb_helper_fill_var()
> in drm_fb_helper_fill_info() function.
>
> This saying implicitly that the fbdev-generic is a glue layer which copy
> damage frame buffer data
>
> from the front end(fbdev layer) to its drm backend. It's not a 100%
> replacement its fbdev front end,
>
> rather, it relay on it.
>
>
> > so if we have issue with limit
> > checks blowing up it makes more sense to check them against drm limits.
> > Plus a lot more people understand those than fbdev. They should all match
> > anyway, or if they dont, we have a bug.
>
> Yes, this is really what I'm worry about.
>
> I see that members of struct fb_var_screeninfo can be changed by
> user-space. For example, xoffset and yoffset.
>
> There is no change about 'info->var.xres' and 'info->var.yres' from the
> userspace,
>
> therefore, they should all match in practice.
>
>
> User-space can choose a use a smaller dispaly area than 'var.xres x
> var.yres',
>
> but that is implemented with 'var.xoffset' and 'var.xoffset'.
>
> But consider that the name 'var', which may stand for 'variation' or
> 'vary'. This is terrifying.
>
> I imagine, with a shadow buffer, the front end can do any modeset on the
> runtime freely,
>
> including change the format of frame buffer on the runtime. Just do not
> out-of-bound.
>
> The middle do the conversion on the fly.
>
>
> We might also create double shadow buffer size to allow the front end to
> pan?
Yeah so the front should be able to pan. And the front-end can
actually make xres/yres smalle than drm_fb->height/width, so we _have_
to use the fb side of things. Otherwise it's a bug I just realized.
The xres_virtual/yres_virtual should always match drm_fb sizes (but
we've had bugs in the past for that, only recently fixed all in
linux-next), because that's supposed to be the max size. And since we
never reallocate the fbdev emulation fb (at least with the current
code) this should never change.
But fundamentally you're bringing up a very good point, we've had
piles of bugs in the past with not properly validating the fbdev side
information in info->var, and a bunch of resulting bugs. So validating
against the drm side of things should be a bit more robust.
It's kinda the same we do for legacy kms ioctls: We translate that to
atomic kms as fast as possible, and then do the entire subsequent
validation with atomic kms data structures.
-Daniel
> > The thing is, if you change this
> > further to just pass the drm_framebuffer, then this 100% becomes a drm
> > function, which could be used by anything in drm really.
>
> I agree with you.
>
> If I use fb_width/fb_height directly and bypassing 'info->var.xres" and
> "info->var.yres",
>
> the code style diverged then. As far as I am understanding, the clip
> happen on
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
Hi,
On 2023/4/14 04:01, Daniel Vetter wrote:
On Thu, Apr 13, 2023 at 09:20:23PM +0200, Thomas Zimmermann wrote:
Hi
Am 13.04.23 um 20:56 schrieb Daniel Vetter:
[...]
This should switch the existing code over to using drm_framebuffer instead
of fbdev:
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index ef4eb8b12766..99ca69dd432f 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -647,22 +647,26 @@ static void drm_fb_helper_damage(struct drm_fb_helper
*helper, u32 x, u32 y,
static void drm_fb_helper_memory_range_to_clip(struct fb_info *info, off_t
off, size_t len,
struct drm_rect *clip)
{
+ struct drm_fb_helper *helper = info->par;
+
off_t end = off + len;
u32 x1 = 0;
u32 y1 = off / info->fix.line_length;
- u32 x2 = info->var.xres;
- u32 y2 = DIV_ROUND_UP(end, info->fix.line_length);
+ u32 x2 = helper->fb->height;
+ unsigned stride = helper->fb->pitches[0];
+ u32 y2 = DIV_ROUND_UP(end, stride);
+ int bpp = drm_format_info_bpp(helper->fb->format, 0);
Please DONT do that. The code here is fbdev code and shouldn't bother about
DRM data structures. Actually, it shouldn't be here: a number of fbdev
drivers with deferred I/O contain similar code and the fbdev module should
provide us with a helper. (I think I even had some patches somewhere.)
Well my thinking is that it's a drm driver,
Yes, I actually agree with this, and the code looks quite good. And I
really want to adopt it.
Because here is DRM, we should emulate the fbdev in the DRM's way.
The DRM is really the big brother on the behind of emulated fbdev,
who provide the real displayable backing memory and scant out engine to
display such a buffer.
But currently, the fact is, drm_fb_helper.c still initializes lots of
data structure come from fbdev world.
For example, the drm_fb_helper_fill_fix() and drm_fb_helper_fill_var()
in drm_fb_helper_fill_info() function.
This saying implicitly that the fbdev-generic is a glue layer which copy
damage frame buffer data
from the front end(fbdev layer) to its drm backend. It's not a 100%
replacement its fbdev front end,
rather, it relay on it.
so if we have issue with limit
checks blowing up it makes more sense to check them against drm limits.
Plus a lot more people understand those than fbdev. They should all match
anyway, or if they dont, we have a bug.
Yes, this is really what I'm worry about.
I see that members of struct fb_var_screeninfo can be changed by
user-space. For example, xoffset and yoffset.
There is no change about 'info->var.xres' and 'info->var.yres' from the
userspace,
therefore, they should all match in practice.
User-space can choose a use a smaller dispaly area than 'var.xres x
var.yres',
but that is implemented with 'var.xoffset' and 'var.xoffset'.
But consider that the name 'var', which may stand for 'variation' or
'vary'. This is terrifying.
I imagine, with a shadow buffer, the front end can do any modeset on the
runtime freely,
including change the format of frame buffer on the runtime. Just do not
out-of-bound.
The middle do the conversion on the fly.
We might also create double shadow buffer size to allow the front end to
pan?
The thing is, if you change this
further to just pass the drm_framebuffer, then this 100% becomes a drm
function, which could be used by anything in drm really.
I agree with you.
If I use fb_width/fb_height directly and bypassing 'info->var.xres" and
"info->var.yres",
the code style diverged then. As far as I am understanding, the clip
happen on the front end,
the actual damage update happen at back end.
Using the data structure come with the front end is more reasonable for
current implement.
But also *shrug*.
I can convert this single function to 100% drm with another patch.
But, maybe there also have other functions are not 100% drm
I would like do something to help achieve this in the future,
let me help to fix this bug first?
-Daniel
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
On Thu, Apr 13, 2023 at 09:20:23PM +0200, Thomas Zimmermann wrote:
> Hi
>
> Am 13.04.23 um 20:56 schrieb Daniel Vetter:
> [...]
> >
> > This should switch the existing code over to using drm_framebuffer instead
> > of fbdev:
> >
> >
> > diff --git a/drivers/gpu/drm/drm_fb_helper.c
> > b/drivers/gpu/drm/drm_fb_helper.c
> > index ef4eb8b12766..99ca69dd432f 100644
> > --- a/drivers/gpu/drm/drm_fb_helper.c
> > +++ b/drivers/gpu/drm/drm_fb_helper.c
> > @@ -647,22 +647,26 @@ static void drm_fb_helper_damage(struct drm_fb_helper
> > *helper, u32 x, u32 y,
> > static void drm_fb_helper_memory_range_to_clip(struct fb_info *info,
> > off_t off, size_t len,
> >struct drm_rect *clip)
> > {
> > + struct drm_fb_helper *helper = info->par;
> > +
> > off_t end = off + len;
> > u32 x1 = 0;
> > u32 y1 = off / info->fix.line_length;
> > - u32 x2 = info->var.xres;
> > - u32 y2 = DIV_ROUND_UP(end, info->fix.line_length);
> > + u32 x2 = helper->fb->height;
> > + unsigned stride = helper->fb->pitches[0];
> > + u32 y2 = DIV_ROUND_UP(end, stride);
> > + int bpp = drm_format_info_bpp(helper->fb->format, 0);
>
> Please DONT do that. The code here is fbdev code and shouldn't bother about
> DRM data structures. Actually, it shouldn't be here: a number of fbdev
> drivers with deferred I/O contain similar code and the fbdev module should
> provide us with a helper. (I think I even had some patches somewhere.)
Well my thinking is that it's a drm driver, so if we have issue with limit
checks blowing up it makes more sense to check them against drm limits.
Plus a lot more people understand those than fbdev. They should all match
anyway, or if they dont, we have a bug. The thing is, if you change this
further to just pass the drm_framebuffer, then this 100% becomes a drm
function, which could be used by anything in drm really.
But also *shrug*.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
Hi
Am 13.04.23 um 20:56 schrieb Daniel Vetter:
[...]
This should switch the existing code over to using drm_framebuffer instead
of fbdev:
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index ef4eb8b12766..99ca69dd432f 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -647,22 +647,26 @@ static void drm_fb_helper_damage(struct drm_fb_helper
*helper, u32 x, u32 y,
static void drm_fb_helper_memory_range_to_clip(struct fb_info *info, off_t
off, size_t len,
struct drm_rect *clip)
{
+ struct drm_fb_helper *helper = info->par;
+
off_t end = off + len;
u32 x1 = 0;
u32 y1 = off / info->fix.line_length;
- u32 x2 = info->var.xres;
- u32 y2 = DIV_ROUND_UP(end, info->fix.line_length);
+ u32 x2 = helper->fb->height;
+ unsigned stride = helper->fb->pitches[0];
+ u32 y2 = DIV_ROUND_UP(end, stride);
+ int bpp = drm_format_info_bpp(helper->fb->format, 0);
Please DONT do that. The code here is fbdev code and shouldn't bother
about DRM data structures. Actually, it shouldn't be here: a number of
fbdev drivers with deferred I/O contain similar code and the fbdev
module should provide us with a helper. (I think I even had some patches
somewhere.)
Best regards
Thomas
if ((y2 - y1) == 1) {
/*
* We've only written to a single scanline. Try to reduce
* the number of horizontal pixels that need an update.
*/
- off_t bit_off = (off % info->fix.line_length) * 8;
- off_t bit_end = (end % info->fix.line_length) * 8;
+ off_t bit_off = (off % stride) * 8;
+ off_t bit_end = (end % stride) * 8;
- x1 = bit_off / info->var.bits_per_pixel;
- x2 = DIV_ROUND_UP(bit_end, info->var.bits_per_pixel);
+ x1 = bit_off / bpp;
+ x2 = DIV_ROUND_UP(bit_end, bpp);
}
drm_rect_init(clip, x1, y1, x2 - x1, y2 - y1);
+ screen_size = sizes->surface_height * buffer->fb->pitches[0];
+
screen_buffer = vzalloc(screen_size);
if (!screen_buffer) {
ret = -ENOMEM;
Cheers, Daniel
--
2.25.1
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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Description: OpenPGP digital signature
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
On Fri, Apr 14, 2023 at 01:00:07AM +0800, Sui Jingfeng wrote: > > On 2023/4/13 23:56, Daniel Vetter wrote: > > On Thu, 13 Apr 2023 at 17:35, Sui Jingfeng <15330273...@189.cn> wrote: > > > Hi, > > > > > > On 2023/4/13 01:44, Daniel Vetter wrote: > > > > On Thu, Apr 13, 2023 at 01:13:37AM +0800, Sui Jingfeng wrote: > > > > > Hi, > > > > > > > > > > On 2023/4/11 22:53, Daniel Vetter wrote: > > > > > > On Sun, Apr 09, 2023 at 09:21:10PM +0800, Sui Jingfeng wrote: > > > > > > > From: Sui Jingfeng > > > > > > > > > > > > > > We should setting the screen buffer size according to the > > > > > > > screen's actual > > > > > > > size, rather than the size of the GEM object backing the front > > > > > > > framebuffer. > > > > > > > The size of GEM buffer is page size aligned, while the size of > > > > > > > active area > > > > > > > of a specific screen is *NOT* necessarily page size aliged. For > > > > > > > example, > > > > > > > 1680x1050, 1600x900, 1440x900, 800x6000 etc. In those case, the > > > > > > > damage rect > > > > > > > computed by drm_fb_helper_memory_range_to_clip() goes out of > > > > > > > bottom bounds > > > > > > > of the display. > > > > > > > > > > > > > > Run fbdev test of IGT on a x86+ast2400 platform with 1680x1050 > > > > > > > resolution > > > > > > > will cause the system hang with the following call trace: > > > > > > > > > > > > > > Oops: [#1] PREEMPT SMP PTI > > > > > > > [IGT] fbdev: starting subtest eof > > > > > > > Workqueue: events drm_fb_helper_damage_work [drm_kms_helper] > > > > > > > [IGT] fbdev: starting subtest nullptr > > > > > > > > > > > > > > RIP: 0010:memcpy_erms+0xa/0x20 > > > > > > > RSP: 0018:a17d40167d98 EFLAGS: 00010246 > > > > > > > RAX: a17d4eb7fa80 RBX: a17d40e0aa80 RCX: > > > > > > > 14c0 > > > > > > > RDX: 1a40 RSI: a17d40e0b000 RDI: > > > > > > > a17d4eb8 > > > > > > > RBP: a17d40167e20 R08: R09: > > > > > > > 89522ecff8c0 > > > > > > > R10: a17d4e4c5000 R11: R12: > > > > > > > a17d4eb7fa80 > > > > > > > R13: 1a40 R14: 041a R15: > > > > > > > a17d40167e30 > > > > > > > FS: () GS:89525738() > > > > > > > knlGS: > > > > > > > CS: 0010 DS: ES: CR0: 80050033 > > > > > > > CR2: a17d40e0b000 CR3: 0001eaeca006 CR4: > > > > > > > 001706e0 > > > > > > > Call Trace: > > > > > > > > > > > > > > ? drm_fbdev_generic_helper_fb_dirty+0x207/0x330 > > > > > > > [drm_kms_helper] > > > > > > > drm_fb_helper_damage_work+0x8f/0x170 [drm_kms_helper] > > > > > > > process_one_work+0x21f/0x430 > > > > > > > worker_thread+0x4e/0x3c0 > > > > > > > ? __pfx_worker_thread+0x10/0x10 > > > > > > > kthread+0xf4/0x120 > > > > > > > ? __pfx_kthread+0x10/0x10 > > > > > > > ret_from_fork+0x2c/0x50 > > > > > > > > > > > > > > CR2: a17d40e0b000 > > > > > > > ---[ end trace ]--- > > > > > > > > > > > > > > We also add trival code in this patch to restrict the damage rect > > > > > > > beyond > > > > > > > the last line of the framebuffer. > > > > > > Nice catch! > > > > >:) > > > > > > > Signed-off-by: Sui Jingfeng > > > > > > > --- > > > > > > > drivers/gpu/drm/drm_fb_helper.c | 2 +- > > > > > > > drivers/gpu/drm/drm_fbdev_generic.c | 2 ++ > > > > > > > 2 files changed, 3 insertions(+), 1 deletion(-) > > > > > > > > > > > > > > diff --git a/drivers/gpu/drm/drm_fb_helper.c > > > > > > > b/drivers/gpu/drm/drm_fb_helper.c > > > > > > > index 64458982be40..a2b749372759 100644 > > > > > > > --- a/drivers/gpu/drm/drm_fb_helper.c > > > > > > > +++ b/drivers/gpu/drm/drm_fb_helper.c > > > > > > > @@ -645,7 +645,7 @@ static void > > > > > > > drm_fb_helper_memory_range_to_clip(struct fb_info *info, off_t > > > > > > > off, > > > > > > > u32 x1 = 0; > > > > > > > u32 y1 = off / info->fix.line_length; > > > > > > > u32 x2 = info->var.xres; > > > > > > > - u32 y2 = DIV_ROUND_UP(end, info->fix.line_length); > > > > > > > + u32 y2 = min_t(u32, DIV_ROUND_UP(end, info->fix.line_length), > > > > > > > info->var.yres); > > > > > > So for additional robustness I think it'd be good if we change the > > > > > > entire > > > > > > computation here to use drm_framebuffer data and not fb_info data, > > > > > > because > > > > > > fundamentally that's what the drm kms code consumes. It should all > > > > > > match > > > > > > anyway, but I think it makes the code more obviously correct. > > > > > > > > > > > > So in the entire function instead of looking at fb_info->fix we > > > > > > should > > > > > > probably look at > > > > > > > > > > > > struct drm_fb_helper *helper = info->par; > > > > > > > > > > > > And then helper->fb->pitches[0] and
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
On 2023/4/13 23:56, Daniel Vetter wrote:
On Thu, 13 Apr 2023 at 17:35, Sui Jingfeng <15330273...@189.cn> wrote:
Hi,
On 2023/4/13 01:44, Daniel Vetter wrote:
On Thu, Apr 13, 2023 at 01:13:37AM +0800, Sui Jingfeng wrote:
Hi,
On 2023/4/11 22:53, Daniel Vetter wrote:
On Sun, Apr 09, 2023 at 09:21:10PM +0800, Sui Jingfeng wrote:
From: Sui Jingfeng
We should setting the screen buffer size according to the screen's actual
size, rather than the size of the GEM object backing the front framebuffer.
The size of GEM buffer is page size aligned, while the size of active area
of a specific screen is *NOT* necessarily page size aliged. For example,
1680x1050, 1600x900, 1440x900, 800x6000 etc. In those case, the damage rect
computed by drm_fb_helper_memory_range_to_clip() goes out of bottom bounds
of the display.
Run fbdev test of IGT on a x86+ast2400 platform with 1680x1050 resolution
will cause the system hang with the following call trace:
Oops: [#1] PREEMPT SMP PTI
[IGT] fbdev: starting subtest eof
Workqueue: events drm_fb_helper_damage_work [drm_kms_helper]
[IGT] fbdev: starting subtest nullptr
RIP: 0010:memcpy_erms+0xa/0x20
RSP: 0018:a17d40167d98 EFLAGS: 00010246
RAX: a17d4eb7fa80 RBX: a17d40e0aa80 RCX: 14c0
RDX: 1a40 RSI: a17d40e0b000 RDI: a17d4eb8
RBP: a17d40167e20 R08: R09: 89522ecff8c0
R10: a17d4e4c5000 R11: R12: a17d4eb7fa80
R13: 1a40 R14: 041a R15: a17d40167e30
FS: () GS:89525738()
knlGS:
CS: 0010 DS: ES: CR0: 80050033
CR2: a17d40e0b000 CR3: 0001eaeca006 CR4: 001706e0
Call Trace:
? drm_fbdev_generic_helper_fb_dirty+0x207/0x330 [drm_kms_helper]
drm_fb_helper_damage_work+0x8f/0x170 [drm_kms_helper]
process_one_work+0x21f/0x430
worker_thread+0x4e/0x3c0
? __pfx_worker_thread+0x10/0x10
kthread+0xf4/0x120
? __pfx_kthread+0x10/0x10
ret_from_fork+0x2c/0x50
CR2: a17d40e0b000
---[ end trace ]---
We also add trival code in this patch to restrict the damage rect beyond
the last line of the framebuffer.
Nice catch!
:)
Signed-off-by: Sui Jingfeng
---
drivers/gpu/drm/drm_fb_helper.c | 2 +-
drivers/gpu/drm/drm_fbdev_generic.c | 2 ++
2 files changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 64458982be40..a2b749372759 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -645,7 +645,7 @@ static void drm_fb_helper_memory_range_to_clip(struct
fb_info *info, off_t off,
u32 x1 = 0;
u32 y1 = off / info->fix.line_length;
u32 x2 = info->var.xres;
- u32 y2 = DIV_ROUND_UP(end, info->fix.line_length);
+ u32 y2 = min_t(u32, DIV_ROUND_UP(end, info->fix.line_length),
info->var.yres);
So for additional robustness I think it'd be good if we change the entire
computation here to use drm_framebuffer data and not fb_info data, because
fundamentally that's what the drm kms code consumes. It should all match
anyway, but I think it makes the code more obviously correct.
So in the entire function instead of looking at fb_info->fix we should
probably look at
struct drm_fb_helper *helper = info->par;
And then helper->fb->pitches[0] and helper->fb->height.
If you agree would be great if you can please respin with that (and the
commit message augmented to explain why we do the change)?
Yes, I'm agree.
Thank you for guidance, I will refine this patch with `helper = info->par`.
I will send a v2 when I finished.
if ((y2 - y1) == 1) {
/*
diff --git a/drivers/gpu/drm/drm_fbdev_generic.c
b/drivers/gpu/drm/drm_fbdev_generic.c
index 8e5148bf40bb..a6daecb5f640 100644
--- a/drivers/gpu/drm/drm_fbdev_generic.c
+++ b/drivers/gpu/drm/drm_fbdev_generic.c
@@ -95,6 +95,8 @@ static int drm_fbdev_generic_helper_fb_probe(struct
drm_fb_helper *fb_helper,
fb_helper->fb = buffer->fb;
screen_size = buffer->gem->size;
I guess you forgot to remove this line here?
Yes, this line should be removed in this patch. I overlooked this, sorry.
Also I'm not understanding
why this matters, I think you're fix only needs the above chunk, not this
one? If I got this right then please drop this part, there's drivers which
only use drm_fb_helper.c but not drm_fbdev_generic.c, and from what I can
tell they all still set the gem buffer size here.
If otoh we need this too, then there's a few more places that need to be
fixed.
I think we need this line, otherwise wrapped around will be happen.
Because I found that the value of variable`y1` will be larger in number than
the variable `y2` by 1,
which are computed in drm_fb_helper_memory_range_to_clip().
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
On Thu, 13 Apr 2023 at 17:35, Sui Jingfeng <15330273...@189.cn> wrote:
>
> Hi,
>
> On 2023/4/13 01:44, Daniel Vetter wrote:
> > On Thu, Apr 13, 2023 at 01:13:37AM +0800, Sui Jingfeng wrote:
> >> Hi,
> >>
> >> On 2023/4/11 22:53, Daniel Vetter wrote:
> >>> On Sun, Apr 09, 2023 at 09:21:10PM +0800, Sui Jingfeng wrote:
> From: Sui Jingfeng
>
> We should setting the screen buffer size according to the screen's actual
> size, rather than the size of the GEM object backing the front
> framebuffer.
> The size of GEM buffer is page size aligned, while the size of active
> area
> of a specific screen is *NOT* necessarily page size aliged. For example,
> 1680x1050, 1600x900, 1440x900, 800x6000 etc. In those case, the damage
> rect
> computed by drm_fb_helper_memory_range_to_clip() goes out of bottom
> bounds
> of the display.
>
> Run fbdev test of IGT on a x86+ast2400 platform with 1680x1050 resolution
> will cause the system hang with the following call trace:
>
> Oops: [#1] PREEMPT SMP PTI
> [IGT] fbdev: starting subtest eof
> Workqueue: events drm_fb_helper_damage_work [drm_kms_helper]
> [IGT] fbdev: starting subtest nullptr
>
> RIP: 0010:memcpy_erms+0xa/0x20
> RSP: 0018:a17d40167d98 EFLAGS: 00010246
> RAX: a17d4eb7fa80 RBX: a17d40e0aa80 RCX: 14c0
> RDX: 1a40 RSI: a17d40e0b000 RDI: a17d4eb8
> RBP: a17d40167e20 R08: R09: 89522ecff8c0
> R10: a17d4e4c5000 R11: R12: a17d4eb7fa80
> R13: 1a40 R14: 041a R15: a17d40167e30
> FS: () GS:89525738()
> knlGS:
> CS: 0010 DS: ES: CR0: 80050033
> CR2: a17d40e0b000 CR3: 0001eaeca006 CR4: 001706e0
> Call Trace:
>
> ? drm_fbdev_generic_helper_fb_dirty+0x207/0x330 [drm_kms_helper]
> drm_fb_helper_damage_work+0x8f/0x170 [drm_kms_helper]
> process_one_work+0x21f/0x430
> worker_thread+0x4e/0x3c0
> ? __pfx_worker_thread+0x10/0x10
> kthread+0xf4/0x120
> ? __pfx_kthread+0x10/0x10
> ret_from_fork+0x2c/0x50
>
> CR2: a17d40e0b000
> ---[ end trace ]---
>
> We also add trival code in this patch to restrict the damage rect beyond
> the last line of the framebuffer.
> >>> Nice catch!
> >> :)
> Signed-off-by: Sui Jingfeng
> ---
> drivers/gpu/drm/drm_fb_helper.c | 2 +-
> drivers/gpu/drm/drm_fbdev_generic.c | 2 ++
> 2 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c
> b/drivers/gpu/drm/drm_fb_helper.c
> index 64458982be40..a2b749372759 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -645,7 +645,7 @@ static void
> drm_fb_helper_memory_range_to_clip(struct fb_info *info, off_t off,
> u32 x1 = 0;
> u32 y1 = off / info->fix.line_length;
> u32 x2 = info->var.xres;
> - u32 y2 = DIV_ROUND_UP(end, info->fix.line_length);
> + u32 y2 = min_t(u32, DIV_ROUND_UP(end, info->fix.line_length),
> info->var.yres);
> >>> So for additional robustness I think it'd be good if we change the entire
> >>> computation here to use drm_framebuffer data and not fb_info data, because
> >>> fundamentally that's what the drm kms code consumes. It should all match
> >>> anyway, but I think it makes the code more obviously correct.
> >>>
> >>> So in the entire function instead of looking at fb_info->fix we should
> >>> probably look at
> >>>
> >>> struct drm_fb_helper *helper = info->par;
> >>>
> >>> And then helper->fb->pitches[0] and helper->fb->height.
> >>>
> >>> If you agree would be great if you can please respin with that (and the
> >>> commit message augmented to explain why we do the change)?
> >> Yes, I'm agree.
> >>
> >> Thank you for guidance, I will refine this patch with `helper = info->par`.
> >>
> >> I will send a v2 when I finished.
> >>
> if ((y2 - y1) == 1) {
> /*
> diff --git a/drivers/gpu/drm/drm_fbdev_generic.c
> b/drivers/gpu/drm/drm_fbdev_generic.c
> index 8e5148bf40bb..a6daecb5f640 100644
> --- a/drivers/gpu/drm/drm_fbdev_generic.c
> +++ b/drivers/gpu/drm/drm_fbdev_generic.c
> @@ -95,6 +95,8 @@ static int drm_fbdev_generic_helper_fb_probe(struct
> drm_fb_helper *fb_helper,
> fb_helper->fb = buffer->fb;
> screen_size = buffer->gem->size;
> >>> I guess you forgot to remove this line here?
> >> Yes, this line should be removed in this patch. I overlooked this, sorry.
>
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
Hi,
On 2023/4/13 01:44, Daniel Vetter wrote:
On Thu, Apr 13, 2023 at 01:13:37AM +0800, Sui Jingfeng wrote:
Hi,
On 2023/4/11 22:53, Daniel Vetter wrote:
On Sun, Apr 09, 2023 at 09:21:10PM +0800, Sui Jingfeng wrote:
From: Sui Jingfeng
We should setting the screen buffer size according to the screen's actual
size, rather than the size of the GEM object backing the front framebuffer.
The size of GEM buffer is page size aligned, while the size of active area
of a specific screen is *NOT* necessarily page size aliged. For example,
1680x1050, 1600x900, 1440x900, 800x6000 etc. In those case, the damage rect
computed by drm_fb_helper_memory_range_to_clip() goes out of bottom bounds
of the display.
Run fbdev test of IGT on a x86+ast2400 platform with 1680x1050 resolution
will cause the system hang with the following call trace:
Oops: [#1] PREEMPT SMP PTI
[IGT] fbdev: starting subtest eof
Workqueue: events drm_fb_helper_damage_work [drm_kms_helper]
[IGT] fbdev: starting subtest nullptr
RIP: 0010:memcpy_erms+0xa/0x20
RSP: 0018:a17d40167d98 EFLAGS: 00010246
RAX: a17d4eb7fa80 RBX: a17d40e0aa80 RCX: 14c0
RDX: 1a40 RSI: a17d40e0b000 RDI: a17d4eb8
RBP: a17d40167e20 R08: R09: 89522ecff8c0
R10: a17d4e4c5000 R11: R12: a17d4eb7fa80
R13: 1a40 R14: 041a R15: a17d40167e30
FS: () GS:89525738() knlGS:
CS: 0010 DS: ES: CR0: 80050033
CR2: a17d40e0b000 CR3: 0001eaeca006 CR4: 001706e0
Call Trace:
? drm_fbdev_generic_helper_fb_dirty+0x207/0x330 [drm_kms_helper]
drm_fb_helper_damage_work+0x8f/0x170 [drm_kms_helper]
process_one_work+0x21f/0x430
worker_thread+0x4e/0x3c0
? __pfx_worker_thread+0x10/0x10
kthread+0xf4/0x120
? __pfx_kthread+0x10/0x10
ret_from_fork+0x2c/0x50
CR2: a17d40e0b000
---[ end trace ]---
We also add trival code in this patch to restrict the damage rect beyond
the last line of the framebuffer.
Nice catch!
:)
Signed-off-by: Sui Jingfeng
---
drivers/gpu/drm/drm_fb_helper.c | 2 +-
drivers/gpu/drm/drm_fbdev_generic.c | 2 ++
2 files changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 64458982be40..a2b749372759 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -645,7 +645,7 @@ static void drm_fb_helper_memory_range_to_clip(struct
fb_info *info, off_t off,
u32 x1 = 0;
u32 y1 = off / info->fix.line_length;
u32 x2 = info->var.xres;
- u32 y2 = DIV_ROUND_UP(end, info->fix.line_length);
+ u32 y2 = min_t(u32, DIV_ROUND_UP(end, info->fix.line_length),
info->var.yres);
So for additional robustness I think it'd be good if we change the entire
computation here to use drm_framebuffer data and not fb_info data, because
fundamentally that's what the drm kms code consumes. It should all match
anyway, but I think it makes the code more obviously correct.
So in the entire function instead of looking at fb_info->fix we should
probably look at
struct drm_fb_helper *helper = info->par;
And then helper->fb->pitches[0] and helper->fb->height.
If you agree would be great if you can please respin with that (and the
commit message augmented to explain why we do the change)?
Yes, I'm agree.
Thank you for guidance, I will refine this patch with `helper = info->par`.
I will send a v2 when I finished.
if ((y2 - y1) == 1) {
/*
diff --git a/drivers/gpu/drm/drm_fbdev_generic.c
b/drivers/gpu/drm/drm_fbdev_generic.c
index 8e5148bf40bb..a6daecb5f640 100644
--- a/drivers/gpu/drm/drm_fbdev_generic.c
+++ b/drivers/gpu/drm/drm_fbdev_generic.c
@@ -95,6 +95,8 @@ static int drm_fbdev_generic_helper_fb_probe(struct
drm_fb_helper *fb_helper,
fb_helper->fb = buffer->fb;
screen_size = buffer->gem->size;
I guess you forgot to remove this line here?
Yes, this line should be removed in this patch. I overlooked this, sorry.
Also I'm not understanding
why this matters, I think you're fix only needs the above chunk, not this
one? If I got this right then please drop this part, there's drivers which
only use drm_fb_helper.c but not drm_fbdev_generic.c, and from what I can
tell they all still set the gem buffer size here.
If otoh we need this too, then there's a few more places that need to be
fixed.
I think we need this line, otherwise wrapped around will be happen.
Because I found that the value of variable`y1` will be larger in number than
the variable `y2` by 1,
which are computed in drm_fb_helper_memory_range_to_clip().
This phenomenon will emerged on platforms with large page size or
non page size divisiable display resolution case. Take the LoongArch and
Mips as an example,
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
On Thu, Apr 13, 2023 at 01:13:37AM +0800, Sui Jingfeng wrote:
> Hi,
>
> On 2023/4/11 22:53, Daniel Vetter wrote:
> > On Sun, Apr 09, 2023 at 09:21:10PM +0800, Sui Jingfeng wrote:
> > > From: Sui Jingfeng
> > >
> > > We should setting the screen buffer size according to the screen's actual
> > > size, rather than the size of the GEM object backing the front
> > > framebuffer.
> > > The size of GEM buffer is page size aligned, while the size of active area
> > > of a specific screen is *NOT* necessarily page size aliged. For example,
> > > 1680x1050, 1600x900, 1440x900, 800x6000 etc. In those case, the damage
> > > rect
> > > computed by drm_fb_helper_memory_range_to_clip() goes out of bottom bounds
> > > of the display.
> > >
> > > Run fbdev test of IGT on a x86+ast2400 platform with 1680x1050 resolution
> > > will cause the system hang with the following call trace:
> > >
> > >Oops: [#1] PREEMPT SMP PTI
> > >[IGT] fbdev: starting subtest eof
> > >Workqueue: events drm_fb_helper_damage_work [drm_kms_helper]
> > >[IGT] fbdev: starting subtest nullptr
> > >
> > >RIP: 0010:memcpy_erms+0xa/0x20
> > >RSP: 0018:a17d40167d98 EFLAGS: 00010246
> > >RAX: a17d4eb7fa80 RBX: a17d40e0aa80 RCX: 14c0
> > >RDX: 1a40 RSI: a17d40e0b000 RDI: a17d4eb8
> > >RBP: a17d40167e20 R08: R09: 89522ecff8c0
> > >R10: a17d4e4c5000 R11: R12: a17d4eb7fa80
> > >R13: 1a40 R14: 041a R15: a17d40167e30
> > >FS: () GS:89525738()
> > > knlGS:
> > >CS: 0010 DS: ES: CR0: 80050033
> > >CR2: a17d40e0b000 CR3: 0001eaeca006 CR4: 001706e0
> > >Call Trace:
> > >
> > > ? drm_fbdev_generic_helper_fb_dirty+0x207/0x330 [drm_kms_helper]
> > > drm_fb_helper_damage_work+0x8f/0x170 [drm_kms_helper]
> > > process_one_work+0x21f/0x430
> > > worker_thread+0x4e/0x3c0
> > > ? __pfx_worker_thread+0x10/0x10
> > > kthread+0xf4/0x120
> > > ? __pfx_kthread+0x10/0x10
> > > ret_from_fork+0x2c/0x50
> > >
> > >CR2: a17d40e0b000
> > >---[ end trace ]---
> > >
> > > We also add trival code in this patch to restrict the damage rect beyond
> > > the last line of the framebuffer.
> > Nice catch!
> :)
> > > Signed-off-by: Sui Jingfeng
> > > ---
> > > drivers/gpu/drm/drm_fb_helper.c | 2 +-
> > > drivers/gpu/drm/drm_fbdev_generic.c | 2 ++
> > > 2 files changed, 3 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/gpu/drm/drm_fb_helper.c
> > > b/drivers/gpu/drm/drm_fb_helper.c
> > > index 64458982be40..a2b749372759 100644
> > > --- a/drivers/gpu/drm/drm_fb_helper.c
> > > +++ b/drivers/gpu/drm/drm_fb_helper.c
> > > @@ -645,7 +645,7 @@ static void drm_fb_helper_memory_range_to_clip(struct
> > > fb_info *info, off_t off,
> > > u32 x1 = 0;
> > > u32 y1 = off / info->fix.line_length;
> > > u32 x2 = info->var.xres;
> > > - u32 y2 = DIV_ROUND_UP(end, info->fix.line_length);
> > > + u32 y2 = min_t(u32, DIV_ROUND_UP(end, info->fix.line_length),
> > > info->var.yres);
> > So for additional robustness I think it'd be good if we change the entire
> > computation here to use drm_framebuffer data and not fb_info data, because
> > fundamentally that's what the drm kms code consumes. It should all match
> > anyway, but I think it makes the code more obviously correct.
> >
> > So in the entire function instead of looking at fb_info->fix we should
> > probably look at
> >
> > struct drm_fb_helper *helper = info->par;
> >
> > And then helper->fb->pitches[0] and helper->fb->height.
> >
> > If you agree would be great if you can please respin with that (and the
> > commit message augmented to explain why we do the change)?
>
> Yes, I'm agree.
>
> Thank you for guidance, I will refine this patch with `helper = info->par`.
>
> I will send a v2 when I finished.
>
> > > if ((y2 - y1) == 1) {
> > > /*
> > > diff --git a/drivers/gpu/drm/drm_fbdev_generic.c
> > > b/drivers/gpu/drm/drm_fbdev_generic.c
> > > index 8e5148bf40bb..a6daecb5f640 100644
> > > --- a/drivers/gpu/drm/drm_fbdev_generic.c
> > > +++ b/drivers/gpu/drm/drm_fbdev_generic.c
> > > @@ -95,6 +95,8 @@ static int drm_fbdev_generic_helper_fb_probe(struct
> > > drm_fb_helper *fb_helper,
> > > fb_helper->fb = buffer->fb;
> > > screen_size = buffer->gem->size;
> > I guess you forgot to remove this line here?
>
> Yes, this line should be removed in this patch. I overlooked this, sorry.
>
> > Also I'm not understanding
> > why this matters, I think you're fix only needs the above chunk, not this
> > one? If I got this right then please drop this part, there's drivers which
> > only use drm_fb_helper.c but not drm_fbdev_generic.c, and from what I can
> > tell they all still set the gem
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
On 2023/4/13 01:13, Sui Jingfeng wrote: I finally got reject by drm_fbdev_generic_helper_fb_dirty() with follow code: It finally got rejected by drm_fbdev_generic_helper_fb_dirty() function with follow code:
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
Hi,
On 2023/4/11 22:53, Daniel Vetter wrote:
On Sun, Apr 09, 2023 at 09:21:10PM +0800, Sui Jingfeng wrote:
From: Sui Jingfeng
We should setting the screen buffer size according to the screen's actual
size, rather than the size of the GEM object backing the front framebuffer.
The size of GEM buffer is page size aligned, while the size of active area
of a specific screen is *NOT* necessarily page size aliged. For example,
1680x1050, 1600x900, 1440x900, 800x6000 etc. In those case, the damage rect
computed by drm_fb_helper_memory_range_to_clip() goes out of bottom bounds
of the display.
Run fbdev test of IGT on a x86+ast2400 platform with 1680x1050 resolution
will cause the system hang with the following call trace:
Oops: [#1] PREEMPT SMP PTI
[IGT] fbdev: starting subtest eof
Workqueue: events drm_fb_helper_damage_work [drm_kms_helper]
[IGT] fbdev: starting subtest nullptr
RIP: 0010:memcpy_erms+0xa/0x20
RSP: 0018:a17d40167d98 EFLAGS: 00010246
RAX: a17d4eb7fa80 RBX: a17d40e0aa80 RCX: 14c0
RDX: 1a40 RSI: a17d40e0b000 RDI: a17d4eb8
RBP: a17d40167e20 R08: R09: 89522ecff8c0
R10: a17d4e4c5000 R11: R12: a17d4eb7fa80
R13: 1a40 R14: 041a R15: a17d40167e30
FS: () GS:89525738() knlGS:
CS: 0010 DS: ES: CR0: 80050033
CR2: a17d40e0b000 CR3: 0001eaeca006 CR4: 001706e0
Call Trace:
? drm_fbdev_generic_helper_fb_dirty+0x207/0x330 [drm_kms_helper]
drm_fb_helper_damage_work+0x8f/0x170 [drm_kms_helper]
process_one_work+0x21f/0x430
worker_thread+0x4e/0x3c0
? __pfx_worker_thread+0x10/0x10
kthread+0xf4/0x120
? __pfx_kthread+0x10/0x10
ret_from_fork+0x2c/0x50
CR2: a17d40e0b000
---[ end trace ]---
We also add trival code in this patch to restrict the damage rect beyond
the last line of the framebuffer.
Nice catch!
:)
Signed-off-by: Sui Jingfeng
---
drivers/gpu/drm/drm_fb_helper.c | 2 +-
drivers/gpu/drm/drm_fbdev_generic.c | 2 ++
2 files changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 64458982be40..a2b749372759 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -645,7 +645,7 @@ static void drm_fb_helper_memory_range_to_clip(struct
fb_info *info, off_t off,
u32 x1 = 0;
u32 y1 = off / info->fix.line_length;
u32 x2 = info->var.xres;
- u32 y2 = DIV_ROUND_UP(end, info->fix.line_length);
+ u32 y2 = min_t(u32, DIV_ROUND_UP(end, info->fix.line_length),
info->var.yres);
So for additional robustness I think it'd be good if we change the entire
computation here to use drm_framebuffer data and not fb_info data, because
fundamentally that's what the drm kms code consumes. It should all match
anyway, but I think it makes the code more obviously correct.
So in the entire function instead of looking at fb_info->fix we should
probably look at
struct drm_fb_helper *helper = info->par;
And then helper->fb->pitches[0] and helper->fb->height.
If you agree would be great if you can please respin with that (and the
commit message augmented to explain why we do the change)?
Yes, I'm agree.
Thank you for guidance, I will refine this patch with `helper = info->par`.
I will send a v2 when I finished.
if ((y2 - y1) == 1) {
/*
diff --git a/drivers/gpu/drm/drm_fbdev_generic.c
b/drivers/gpu/drm/drm_fbdev_generic.c
index 8e5148bf40bb..a6daecb5f640 100644
--- a/drivers/gpu/drm/drm_fbdev_generic.c
+++ b/drivers/gpu/drm/drm_fbdev_generic.c
@@ -95,6 +95,8 @@ static int drm_fbdev_generic_helper_fb_probe(struct
drm_fb_helper *fb_helper,
fb_helper->fb = buffer->fb;
screen_size = buffer->gem->size;
I guess you forgot to remove this line here?
Yes, this line should be removed in this patch. I overlooked this, sorry.
Also I'm not understanding
why this matters, I think you're fix only needs the above chunk, not this
one? If I got this right then please drop this part, there's drivers which
only use drm_fb_helper.c but not drm_fbdev_generic.c, and from what I can
tell they all still set the gem buffer size here.
If otoh we need this too, then there's a few more places that need to be
fixed.
I think we need this line, otherwise wrapped around will be happen.
Because I found that the value of variable`y1` will be larger in number
than the variable `y2` by 1,
which are computed in drm_fb_helper_memory_range_to_clip().
This phenomenon will emerged on platforms with large page size or
non page size divisiable display resolution case. Take the LoongArch and
Mips as an example,
the default page size is 16KB(to avoid cache alias). Even with the most
frequently used
1920x1080 screen, the screen_size can not be
Re: [PATCH] drm/fbdev-generic: fix potential out-of-bounds access
On Sun, Apr 09, 2023 at 09:21:10PM +0800, Sui Jingfeng wrote:
> From: Sui Jingfeng
>
> We should setting the screen buffer size according to the screen's actual
> size, rather than the size of the GEM object backing the front framebuffer.
> The size of GEM buffer is page size aligned, while the size of active area
> of a specific screen is *NOT* necessarily page size aliged. For example,
> 1680x1050, 1600x900, 1440x900, 800x6000 etc. In those case, the damage rect
> computed by drm_fb_helper_memory_range_to_clip() goes out of bottom bounds
> of the display.
>
> Run fbdev test of IGT on a x86+ast2400 platform with 1680x1050 resolution
> will cause the system hang with the following call trace:
>
> Oops: [#1] PREEMPT SMP PTI
> [IGT] fbdev: starting subtest eof
> Workqueue: events drm_fb_helper_damage_work [drm_kms_helper]
> [IGT] fbdev: starting subtest nullptr
>
> RIP: 0010:memcpy_erms+0xa/0x20
> RSP: 0018:a17d40167d98 EFLAGS: 00010246
> RAX: a17d4eb7fa80 RBX: a17d40e0aa80 RCX: 14c0
> RDX: 1a40 RSI: a17d40e0b000 RDI: a17d4eb8
> RBP: a17d40167e20 R08: R09: 89522ecff8c0
> R10: a17d4e4c5000 R11: R12: a17d4eb7fa80
> R13: 1a40 R14: 041a R15: a17d40167e30
> FS: () GS:89525738() knlGS:
> CS: 0010 DS: ES: CR0: 80050033
> CR2: a17d40e0b000 CR3: 0001eaeca006 CR4: 001706e0
> Call Trace:
>
>? drm_fbdev_generic_helper_fb_dirty+0x207/0x330 [drm_kms_helper]
>drm_fb_helper_damage_work+0x8f/0x170 [drm_kms_helper]
>process_one_work+0x21f/0x430
>worker_thread+0x4e/0x3c0
>? __pfx_worker_thread+0x10/0x10
>kthread+0xf4/0x120
>? __pfx_kthread+0x10/0x10
>ret_from_fork+0x2c/0x50
>
> CR2: a17d40e0b000
> ---[ end trace ]---
>
> We also add trival code in this patch to restrict the damage rect beyond
> the last line of the framebuffer.
Nice catch!
>
> Signed-off-by: Sui Jingfeng
> ---
> drivers/gpu/drm/drm_fb_helper.c | 2 +-
> drivers/gpu/drm/drm_fbdev_generic.c | 2 ++
> 2 files changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 64458982be40..a2b749372759 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -645,7 +645,7 @@ static void drm_fb_helper_memory_range_to_clip(struct
> fb_info *info, off_t off,
> u32 x1 = 0;
> u32 y1 = off / info->fix.line_length;
> u32 x2 = info->var.xres;
> - u32 y2 = DIV_ROUND_UP(end, info->fix.line_length);
> + u32 y2 = min_t(u32, DIV_ROUND_UP(end, info->fix.line_length),
> info->var.yres);
So for additional robustness I think it'd be good if we change the entire
computation here to use drm_framebuffer data and not fb_info data, because
fundamentally that's what the drm kms code consumes. It should all match
anyway, but I think it makes the code more obviously correct.
So in the entire function instead of looking at fb_info->fix we should
probably look at
struct drm_fb_helper *helper = info->par;
And then helper->fb->pitches[0] and helper->fb->height.
If you agree would be great if you can please respin with that (and the
commit message augmented to explain why we do the change)?
>
> if ((y2 - y1) == 1) {
> /*
> diff --git a/drivers/gpu/drm/drm_fbdev_generic.c
> b/drivers/gpu/drm/drm_fbdev_generic.c
> index 8e5148bf40bb..a6daecb5f640 100644
> --- a/drivers/gpu/drm/drm_fbdev_generic.c
> +++ b/drivers/gpu/drm/drm_fbdev_generic.c
> @@ -95,6 +95,8 @@ static int drm_fbdev_generic_helper_fb_probe(struct
> drm_fb_helper *fb_helper,
> fb_helper->fb = buffer->fb;
>
> screen_size = buffer->gem->size;
I guess you forgot to remove this line here? Also I'm not understanding
why this matters, I think you're fix only needs the above chunk, not this
one? If I got this right then please drop this part, there's drivers which
only use drm_fb_helper.c but not drm_fbdev_generic.c, and from what I can
tell they all still set the gem buffer size here.
If otoh we need this too, then there's a few more places that need to be
fixed.
> + screen_size = sizes->surface_height * buffer->fb->pitches[0];
> +
> screen_buffer = vzalloc(screen_size);
> if (!screen_buffer) {
> ret = -ENOMEM;
Cheers, Daniel
> --
> 2.25.1
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
