Re: [PATCH 05/10] vhost-backend: avoid overflow on memslots_limit
On Fri, Nov 12, 2021 at 09:56:17AM +, Daniel P. Berrangé wrote:
> On Fri, Nov 12, 2021 at 10:46:46AM +0300, Roman Kagan wrote:
> > On Thu, Nov 11, 2021 at 06:59:43PM +0100, Philippe Mathieu-Daudé wrote:
> > > On 11/11/21 16:33, Roman Kagan wrote:
> > > > Fix the (hypothetical) potential problem when the value parsed out of
> > > > the vhost module parameter in sysfs overflows the return value from
> > > > vhost_kernel_memslots_limit.
> > > >
> > > > Signed-off-by: Roman Kagan
> > > > ---
> > > > hw/virtio/vhost-backend.c | 2 +-
> > > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > > >
> > > > diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
> > > > index b65f8f7e97..44f7dbb243 100644
> > > > --- a/hw/virtio/vhost-backend.c
> > > > +++ b/hw/virtio/vhost-backend.c
> > > > @@ -58,7 +58,7 @@ static int vhost_kernel_memslots_limit(struct
> > > > vhost_dev *dev)
> > > > if
> > > > (g_file_get_contents("/sys/module/vhost/parameters/max_mem_regions",
> > > > , NULL, NULL)) {
> > > > uint64_t val = g_ascii_strtoull(s, NULL, 10);
> > >
> > > Would using qemu_strtou64() simplify this?
> >
> > I'm afraid not. None of the existing strtoXX converting functions has
> > the desired output range (0 < retval < INT_MAX), so the following
> > condition will remain necessary anyway; then it doesn't seem to matter
> > which particular parser is used to extract the value which is in the
> > range, so I left the one that was already there to reduce churn.
>
> If qemu_strtou64() can't handle all values in (0 < retval < INT_MAX)
> isn't that a bug in qemu_strtou64 ?
I must have been unclear. It sure can handle all values in this range;
the point is that the range check after it would still be needed, so
switching from g_ascii_strtoull to qemu_strtoXX saves nothing, therefore
I left it as it was.
Thanks,
Roman.
Re: [PATCH 05/10] vhost-backend: avoid overflow on memslots_limit
On Fri, Nov 12, 2021 at 10:46:46AM +0300, Roman Kagan wrote:
> On Thu, Nov 11, 2021 at 06:59:43PM +0100, Philippe Mathieu-Daudé wrote:
> > On 11/11/21 16:33, Roman Kagan wrote:
> > > Fix the (hypothetical) potential problem when the value parsed out of
> > > the vhost module parameter in sysfs overflows the return value from
> > > vhost_kernel_memslots_limit.
> > >
> > > Signed-off-by: Roman Kagan
> > > ---
> > > hw/virtio/vhost-backend.c | 2 +-
> > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
> > > index b65f8f7e97..44f7dbb243 100644
> > > --- a/hw/virtio/vhost-backend.c
> > > +++ b/hw/virtio/vhost-backend.c
> > > @@ -58,7 +58,7 @@ static int vhost_kernel_memslots_limit(struct vhost_dev
> > > *dev)
> > > if
> > > (g_file_get_contents("/sys/module/vhost/parameters/max_mem_regions",
> > > , NULL, NULL)) {
> > > uint64_t val = g_ascii_strtoull(s, NULL, 10);
> >
> > Would using qemu_strtou64() simplify this?
>
> I'm afraid not. None of the existing strtoXX converting functions has
> the desired output range (0 < retval < INT_MAX), so the following
> condition will remain necessary anyway; then it doesn't seem to matter
> which particular parser is used to extract the value which is in the
> range, so I left the one that was already there to reduce churn.
If qemu_strtou64() can't handle all values in (0 < retval < INT_MAX)
isn't that a bug in qemu_strtou64 ?
Regards,
Daniel
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Re: [PATCH 05/10] vhost-backend: avoid overflow on memslots_limit
On Thu, Nov 11, 2021 at 06:59:43PM +0100, Philippe Mathieu-Daudé wrote:
> On 11/11/21 16:33, Roman Kagan wrote:
> > Fix the (hypothetical) potential problem when the value parsed out of
> > the vhost module parameter in sysfs overflows the return value from
> > vhost_kernel_memslots_limit.
> >
> > Signed-off-by: Roman Kagan
> > ---
> > hw/virtio/vhost-backend.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
> > index b65f8f7e97..44f7dbb243 100644
> > --- a/hw/virtio/vhost-backend.c
> > +++ b/hw/virtio/vhost-backend.c
> > @@ -58,7 +58,7 @@ static int vhost_kernel_memslots_limit(struct vhost_dev
> > *dev)
> > if (g_file_get_contents("/sys/module/vhost/parameters/max_mem_regions",
> > , NULL, NULL)) {
> > uint64_t val = g_ascii_strtoull(s, NULL, 10);
>
> Would using qemu_strtou64() simplify this?
I'm afraid not. None of the existing strtoXX converting functions has
the desired output range (0 < retval < INT_MAX), so the following
condition will remain necessary anyway; then it doesn't seem to matter
which particular parser is used to extract the value which is in the
range, so I left the one that was already there to reduce churn.
>
> > -if (!((val == G_MAXUINT64 || !val) && errno)) {
> > +if (val < INT_MAX && val > 0) {
> > g_free(s);
> > return val;
> > }
Thanks,
Roman.
Re: [PATCH 05/10] vhost-backend: avoid overflow on memslots_limit
On 11/11/21 16:33, Roman Kagan wrote:
> Fix the (hypothetical) potential problem when the value parsed out of
> the vhost module parameter in sysfs overflows the return value from
> vhost_kernel_memslots_limit.
>
> Signed-off-by: Roman Kagan
> ---
> hw/virtio/vhost-backend.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
> index b65f8f7e97..44f7dbb243 100644
> --- a/hw/virtio/vhost-backend.c
> +++ b/hw/virtio/vhost-backend.c
> @@ -58,7 +58,7 @@ static int vhost_kernel_memslots_limit(struct vhost_dev
> *dev)
> if (g_file_get_contents("/sys/module/vhost/parameters/max_mem_regions",
> , NULL, NULL)) {
> uint64_t val = g_ascii_strtoull(s, NULL, 10);
Would using qemu_strtou64() simplify this?
> -if (!((val == G_MAXUINT64 || !val) && errno)) {
> +if (val < INT_MAX && val > 0) {
> g_free(s);
> return val;
> }
>
[PATCH 05/10] vhost-backend: avoid overflow on memslots_limit
Fix the (hypothetical) potential problem when the value parsed out of
the vhost module parameter in sysfs overflows the return value from
vhost_kernel_memslots_limit.
Signed-off-by: Roman Kagan
---
hw/virtio/vhost-backend.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
index b65f8f7e97..44f7dbb243 100644
--- a/hw/virtio/vhost-backend.c
+++ b/hw/virtio/vhost-backend.c
@@ -58,7 +58,7 @@ static int vhost_kernel_memslots_limit(struct vhost_dev *dev)
if (g_file_get_contents("/sys/module/vhost/parameters/max_mem_regions",
, NULL, NULL)) {
uint64_t val = g_ascii_strtoull(s, NULL, 10);
-if (!((val == G_MAXUINT64 || !val) && errno)) {
+if (val < INT_MAX && val > 0) {
g_free(s);
return val;
}
--
2.33.1
