Add a limit to 'config->vq_num' which is user controlled data which
comes from an vduse_ioctl to prevent large memory allocations.
This is found using static analysis with smatch.
Suggested-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Harshit Mogalapalli <[email protected]>
---
v1->v2: Change title of the commit and description, add a limit to
vq_num.
Note: I think here 0xffff is the max size of vring = no: of vqueues.
Only compile and boot tested.
---
drivers/vdpa/vdpa_user/vduse_dev.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
index 35dceee3ed56..31017ebc4d7c 100644
--- a/drivers/vdpa/vdpa_user/vduse_dev.c
+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
@@ -1440,6 +1440,9 @@ static bool vduse_validate_config(struct vduse_dev_config *config)
if (config->config_size > PAGE_SIZE)
return false;
+ if (config->vq_num > 0xffff)
+ return false;
+
if (!device_is_allowed(config->device_id))
return false;
--
2.38.1
On Mon, Nov 28, 2022 at 12:36:26AM -0800, Harshit Mogalapalli wrote:
>Add a limit to 'config->vq_num' which is user controlled data which
>comes from an vduse_ioctl to prevent large memory allocations.
>
>This is found using static analysis with smatch.
>
>Suggested-by: Michael S. Tsirkin <[email protected]>
>Signed-off-by: Harshit Mogalapalli <[email protected]>
>---
>v1->v2: Change title of the commit and description, add a limit to
> vq_num.
>
>Note: I think here 0xffff is the max size of vring = no: of vqueues.
>Only compile and boot tested.
>---
> drivers/vdpa/vdpa_user/vduse_dev.c | 3 +++
> 1 file changed, 3 insertions(+)
>
>diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
>index 35dceee3ed56..31017ebc4d7c 100644
>--- a/drivers/vdpa/vdpa_user/vduse_dev.c
>+++ b/drivers/vdpa/vdpa_user/vduse_dev.c
>@@ -1440,6 +1440,9 @@ static bool vduse_validate_config(struct vduse_dev_config *config)
> if (config->config_size > PAGE_SIZE)
> return false;
>
>+ if (config->vq_num > 0xffff)
What about using U16_MAX here?
Thanks,
Stefano
>+ return false;
>+
> if (!device_is_allowed(config->device_id))
> return false;
>
>--
>2.38.1
>
On Mon, Nov 28, 2022 at 01:58:00PM +0300, Dan Carpenter wrote:
>On Mon, Nov 28, 2022 at 11:53:12AM +0100, Stefano Garzarella wrote:
>> On Mon, Nov 28, 2022 at 12:36:26AM -0800, Harshit Mogalapalli wrote:
>> > Add a limit to 'config->vq_num' which is user controlled data which
>> > comes from an vduse_ioctl to prevent large memory allocations.
>> >
>> > This is found using static analysis with smatch.
>> >
>> > Suggested-by: Michael S. Tsirkin <[email protected]>
>> > Signed-off-by: Harshit Mogalapalli <[email protected]>
>> > ---
>> > v1->v2: Change title of the commit and description, add a limit to
>> > vq_num.
>> >
>> > Note: I think here 0xffff is the max size of vring = no: of vqueues.
>> > Only compile and boot tested.
>> > ---
>> > drivers/vdpa/vdpa_user/vduse_dev.c | 3 +++
>> > 1 file changed, 3 insertions(+)
>> >
>> > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
>> > index 35dceee3ed56..31017ebc4d7c 100644
>> > --- a/drivers/vdpa/vdpa_user/vduse_dev.c
>> > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
>> > @@ -1440,6 +1440,9 @@ static bool vduse_validate_config(struct vduse_dev_config *config)
>> > if (config->config_size > PAGE_SIZE)
>> > return false;
>> >
>> > + if (config->vq_num > 0xffff)
>>
>> What about using U16_MAX here?
>
>Where is the ->vq_num stored in a u16? I looked for this but didn't
>see it.
I thought vq_num referred to the number of elements in the vq (like
.get_vq_num_max), since this patch wants to limit to 0xffff.
But it actually refers to the number of virtqueue, so @Harshit why do we
limit it to 0xffff?
Maybe we should explain it in the commit message or in a comment.
Thanks,
Stefano
On Mon, Nov 28, 2022 at 11:53:12AM +0100, Stefano Garzarella wrote:
> On Mon, Nov 28, 2022 at 12:36:26AM -0800, Harshit Mogalapalli wrote:
> > Add a limit to 'config->vq_num' which is user controlled data which
> > comes from an vduse_ioctl to prevent large memory allocations.
> >
> > This is found using static analysis with smatch.
> >
> > Suggested-by: Michael S. Tsirkin <[email protected]>
> > Signed-off-by: Harshit Mogalapalli <[email protected]>
> > ---
> > v1->v2: Change title of the commit and description, add a limit to
> > vq_num.
> >
> > Note: I think here 0xffff is the max size of vring = no: of vqueues.
> > Only compile and boot tested.
> > ---
> > drivers/vdpa/vdpa_user/vduse_dev.c | 3 +++
> > 1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> > index 35dceee3ed56..31017ebc4d7c 100644
> > --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> > @@ -1440,6 +1440,9 @@ static bool vduse_validate_config(struct vduse_dev_config *config)
> > if (config->config_size > PAGE_SIZE)
> > return false;
> >
> > + if (config->vq_num > 0xffff)
>
> What about using U16_MAX here?
Where is the ->vq_num stored in a u16? I looked for this but didn't
see it.
regards,
dan carpenter
On 28/11/22 4:43 pm, Stefano Garzarella wrote:
> On Mon, Nov 28, 2022 at 01:58:00PM +0300, Dan Carpenter wrote:
>> On Mon, Nov 28, 2022 at 11:53:12AM +0100, Stefano Garzarella wrote:
>>> On Mon, Nov 28, 2022 at 12:36:26AM -0800, Harshit Mogalapalli wrote:
>>> > Add a limit to 'config->vq_num' which is user controlled data which
>>> > comes from an vduse_ioctl to prevent large memory allocations.
>>> >
>>> > This is found using static analysis with smatch.
>>> >
>>> > Suggested-by: Michael S. Tsirkin <[email protected]>
>>> > Signed-off-by: Harshit Mogalapalli <[email protected]>
>>> > ---
>>> > v1->v2: Change title of the commit and description, add a limit to
>>> > vq_num.
>>> >
>>> > Note: I think here 0xffff is the max size of vring = no: of vqueues.
>>> > Only compile and boot tested.
>>> > ---
>>> > drivers/vdpa/vdpa_user/vduse_dev.c | 3 +++
>>> > 1 file changed, 3 insertions(+)
>>> >
>>> > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c
>>> b/drivers/vdpa/vdpa_user/vduse_dev.c
>>> > index 35dceee3ed56..31017ebc4d7c 100644
>>> > --- a/drivers/vdpa/vdpa_user/vduse_dev.c
>>> > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
>>> > @@ -1440,6 +1440,9 @@ static bool vduse_validate_config(struct
>>> vduse_dev_config *config)
>>> > if (config->config_size > PAGE_SIZE)
>>> > return false;
>>> >
>>> > + if (config->vq_num > 0xffff)
>>>
>>> What about using U16_MAX here?
>>
>> Where is the ->vq_num stored in a u16? I looked for this but didn't
>> see it.
>
> I thought vq_num referred to the number of elements in the vq (like
> .get_vq_num_max), since this patch wants to limit to 0xffff.
>
> But it actually refers to the number of virtqueue, so @Harshit why do we
> limit it to 0xffff?
>
Hi Stefano,
I may be incorrect about the details of this driver, my v1 was purely
based on static analysis, Micheal suggested me to put a limit of 0xffff
on vq_num. I really don't know about the driver, while I was searching
other parts of code, I thought 0xffff is based vring size, I have asked
the same question on v1 today.
Ref to v1:
https://lore.kernel.org/all/[email protected]/
> Maybe we should explain it in the commit message or in a comment.
>
yeah, we should clarify the limit in commit message, once Micheal shares
about the limit '0xffff), I will add those details and send a next
version if that's okay.
Thanks,
Harshit
> Thanks,
> Stefano
>
On Mon, Nov 28, 2022 at 12:13:10PM +0100, Stefano Garzarella wrote:
> On Mon, Nov 28, 2022 at 01:58:00PM +0300, Dan Carpenter wrote:
> > On Mon, Nov 28, 2022 at 11:53:12AM +0100, Stefano Garzarella wrote:
> > > On Mon, Nov 28, 2022 at 12:36:26AM -0800, Harshit Mogalapalli wrote:
> > > > Add a limit to 'config->vq_num' which is user controlled data which
> > > > comes from an vduse_ioctl to prevent large memory allocations.
> > > >
> > > > This is found using static analysis with smatch.
> > > >
> > > > Suggested-by: Michael S. Tsirkin <[email protected]>
> > > > Signed-off-by: Harshit Mogalapalli <[email protected]>
> > > > ---
> > > > v1->v2: Change title of the commit and description, add a limit to
> > > > vq_num.
> > > >
> > > > Note: I think here 0xffff is the max size of vring = no: of vqueues.
> > > > Only compile and boot tested.
> > > > ---
> > > > drivers/vdpa/vdpa_user/vduse_dev.c | 3 +++
> > > > 1 file changed, 3 insertions(+)
> > > >
> > > > diff --git a/drivers/vdpa/vdpa_user/vduse_dev.c b/drivers/vdpa/vdpa_user/vduse_dev.c
> > > > index 35dceee3ed56..31017ebc4d7c 100644
> > > > --- a/drivers/vdpa/vdpa_user/vduse_dev.c
> > > > +++ b/drivers/vdpa/vdpa_user/vduse_dev.c
> > > > @@ -1440,6 +1440,9 @@ static bool vduse_validate_config(struct vduse_dev_config *config)
> > > > if (config->config_size > PAGE_SIZE)
> > > > return false;
> > > >
> > > > + if (config->vq_num > 0xffff)
> > >
> > > What about using U16_MAX here?
> >
> > Where is the ->vq_num stored in a u16? I looked for this but didn't
> > see it.
>
> I thought vq_num referred to the number of elements in the vq (like
> .get_vq_num_max), since this patch wants to limit to 0xffff.
>
> But it actually refers to the number of virtqueue, so @Harshit why do we
> limit it to 0xffff?
>
> Maybe we should explain it in the commit message or in a comment.
>
> Thanks,
> Stefano
This limit is somewhat arbitrary.
However, currently virtio pci and ccw are limited to a 16 bit vq number.
While MMIO isn't it is also isn't used with lots of VQs due to
current lack of support for per-vq interrupts.
Thus, the 0xffff limit on number of VQs corresponding
to a 16-bit VQ number seems sufficient for now.
Feel free to put the above in a code comment.
--
MST