Re: [PATCH v3 3/4] fbdev: efifb: Cleanup fb_info in .fb_destroy rather than .remove
Hello Andrzej, On 5/6/22 15:07, Andrzej Hajda wrote: > On 06.05.2022 00:05, Javier Martinez Canillas wrote: [snip] >> + >> +framebuffer_release(info); >> + >> if (request_mem_succeeded) >> release_mem_region(info->apertures->ranges[0].base, >> info->apertures->ranges[0].size); > > You are releasing info, then you are using it. > > I suspect it is responsible for multiple failures of Intel CI [1]. > Yes, it is :( sorry about the mess. Ville already reported this to me. I'll post a patch in a minute. I wonder how this didn't happen before since .remove() happens before .fb_destroy() AFAIU... -- Best regards, Javier Martinez Canillas Linux Engineering Red Hat
Re: [PATCH v3 3/4] fbdev: efifb: Cleanup fb_info in .fb_destroy rather than .remove
On 06.05.2022 00:05, Javier Martinez Canillas wrote:
The driver is calling framebuffer_release() in its .remove callback, but
this will cause the struct fb_info to be freed too early. Since it could
be that a reference is still hold to it if user-space opened the fbdev.
This would lead to a use-after-free error if the framebuffer device was
unregistered but later a user-space process tries to close the fbdev fd.
To prevent this, move the framebuffer_release() call to fb_ops.fb_destroy
instead of doing it in the driver's .remove callback.
Strictly speaking, the code flow in the driver is still wrong because all
the hardware cleanupd (i.e: iounmap) should be done in .remove while the
software cleanup (i.e: releasing the framebuffer) should be done in the
.fb_destroy handler. But this at least makes to match the behavior before
commit 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal").
Fixes: 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal")
Suggested-by: Daniel Vetter
Signed-off-by: Javier Martinez Canillas
Reviewed-by: Thomas Zimmermann
Reviewed-by: Daniel Vetter
---
(no changes since v1)
drivers/video/fbdev/efifb.c | 9 -
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
index ea42ba6445b2..cfa3dc0b4eee 100644
--- a/drivers/video/fbdev/efifb.c
+++ b/drivers/video/fbdev/efifb.c
@@ -243,6 +243,10 @@ static void efifb_show_boot_graphics(struct fb_info *info)
static inline void efifb_show_boot_graphics(struct fb_info *info) {}
#endif
+/*
+ * fb_ops.fb_destroy is called by the last put_fb_info() call at the end
+ * of unregister_framebuffer() or fb_release(). Do any cleanup here.
+ */
static void efifb_destroy(struct fb_info *info)
{
if (efifb_pci_dev)
@@ -254,6 +258,9 @@ static void efifb_destroy(struct fb_info *info)
else
memunmap(info->screen_base);
}
+
+ framebuffer_release(info);
+
if (request_mem_succeeded)
release_mem_region(info->apertures->ranges[0].base,
info->apertures->ranges[0].size);
You are releasing info, then you are using it.
I suspect it is responsible for multiple failures of Intel CI [1].
[1]:
http://gfx-ci.fi.intel.com/tree/drm-tip/CI_DRM_11615/fi-adl-ddr5/boot0.txt
Regards
Andrzej
@@ -620,9 +627,9 @@ static int efifb_remove(struct platform_device *pdev)
{
struct fb_info *info = platform_get_drvdata(pdev);
+ /* efifb_destroy takes care of info cleanup */
unregister_framebuffer(info);
sysfs_remove_groups(&pdev->dev.kobj, efifb_groups);
- framebuffer_release(info);
return 0;
}
[PATCH v3 3/4] fbdev: efifb: Cleanup fb_info in .fb_destroy rather than .remove
The driver is calling framebuffer_release() in its .remove callback, but
this will cause the struct fb_info to be freed too early. Since it could
be that a reference is still hold to it if user-space opened the fbdev.
This would lead to a use-after-free error if the framebuffer device was
unregistered but later a user-space process tries to close the fbdev fd.
To prevent this, move the framebuffer_release() call to fb_ops.fb_destroy
instead of doing it in the driver's .remove callback.
Strictly speaking, the code flow in the driver is still wrong because all
the hardware cleanupd (i.e: iounmap) should be done in .remove while the
software cleanup (i.e: releasing the framebuffer) should be done in the
.fb_destroy handler. But this at least makes to match the behavior before
commit 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal").
Fixes: 27599aacbaef ("fbdev: Hot-unplug firmware fb devices on forced removal")
Suggested-by: Daniel Vetter
Signed-off-by: Javier Martinez Canillas
Reviewed-by: Thomas Zimmermann
Reviewed-by: Daniel Vetter
---
(no changes since v1)
drivers/video/fbdev/efifb.c | 9 -
1 file changed, 8 insertions(+), 1 deletion(-)
diff --git a/drivers/video/fbdev/efifb.c b/drivers/video/fbdev/efifb.c
index ea42ba6445b2..cfa3dc0b4eee 100644
--- a/drivers/video/fbdev/efifb.c
+++ b/drivers/video/fbdev/efifb.c
@@ -243,6 +243,10 @@ static void efifb_show_boot_graphics(struct fb_info *info)
static inline void efifb_show_boot_graphics(struct fb_info *info) {}
#endif
+/*
+ * fb_ops.fb_destroy is called by the last put_fb_info() call at the end
+ * of unregister_framebuffer() or fb_release(). Do any cleanup here.
+ */
static void efifb_destroy(struct fb_info *info)
{
if (efifb_pci_dev)
@@ -254,6 +258,9 @@ static void efifb_destroy(struct fb_info *info)
else
memunmap(info->screen_base);
}
+
+ framebuffer_release(info);
+
if (request_mem_succeeded)
release_mem_region(info->apertures->ranges[0].base,
info->apertures->ranges[0].size);
@@ -620,9 +627,9 @@ static int efifb_remove(struct platform_device *pdev)
{
struct fb_info *info = platform_get_drvdata(pdev);
+ /* efifb_destroy takes care of info cleanup */
unregister_framebuffer(info);
sysfs_remove_groups(&pdev->dev.kobj, efifb_groups);
- framebuffer_release(info);
return 0;
}
--
2.35.1
