[PATCH v2] drm/fb-helper: add virtual screen size check to drm_fb_helper_check_var()

[PATCH v2] drm/fb-helper: add virtual screen size check to drm_fb_helper_check_var()

[Andrey Strachuk]

Add virtual screen size check to drm_fb_helper_check_var() in
order to validate userspace input.

Found by Linux Verification Center (linuxtesting.org) with syzkaller.

Signed-off-by: Andrey Strachuk <strochuk@ispras.ru>
Fixes: 785b93ef8c30 ("drm/kms: move driver specific fb common code to helper functions (v2)")
---
 drivers/gpu/drm/drm_fb_helper.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index 2d4cee6a10ff..5c8b211769eb 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -1355,6 +1355,12 @@ int drm_fb_helper_check_var(struct fb_var_screeninfo *var,
 	    (drm_format_info_block_height(fb->format, 0) > 1))
 		return -EINVAL;
 
+	/* verify that virtual resolution >= physical resolution */
+	if (var->xres_virtual < var->xres)
+		var->xres_virtual = var->xres;
+	if (var->yres_virtual < var->yres)
+		var->yres_virtual = var->yres;
+
 	/*
 	 * Changes struct fb_var_screeninfo are currently not pushed back
 	 * to KMS, hence fail if different settings are requested.
-- 
2.25.1

Re: [PATCH v2] drm/fb-helper: add virtual screen size check to drm_fb_helper_check_var()

[Geert Uytterhoeven]

Hi Andrey,

On Thu, Aug 11, 2022 at 4:49 PM Andrey Strachuk <strochuk@ispras.ru> wrote:
> Add virtual screen size check to drm_fb_helper_check_var() in
> order to validate userspace input.
>
> Found by Linux Verification Center (linuxtesting.org) with syzkaller.
>
> Signed-off-by: Andrey Strachuk <strochuk@ispras.ru>

Thanks for the update!

> Fixes: 785b93ef8c30 ("drm/kms: move driver specific fb common code to helper functions (v2)")

I'd drop the Fixes tag completely, as the bug was present in the
intel and radeon drivers before. But probably it doesn't matter, as no one
is gonna backport this to v2.6.31 and earlier ;-)

Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [ldv-project] [PATCH v2] drm/fb-helper: add virtual screen size check to drm_fb_helper_check_var()

[Alexey Khoroshilov]

For v2 I would suggest to update description to something like this:

Make sure that virtual screen size is not less than physical screen one.

and comment to:
    /* make sure that virtual resolution >= physical resolution */

--
Alexey


On 11.08.2022 17:54, Geert Uytterhoeven wrote:
> Hi Andrey,
> 
> On Thu, Aug 11, 2022 at 4:49 PM Andrey Strachuk <strochuk@ispras.ru> wrote:
>> Add virtual screen size check to drm_fb_helper_check_var() in
>> order to validate userspace input.
>>
>> Found by Linux Verification Center (linuxtesting.org) with syzkaller.
>>
>> Signed-off-by: Andrey Strachuk <strochuk@ispras.ru>
> 
> Thanks for the update!
> 
>> Fixes: 785b93ef8c30 ("drm/kms: move driver specific fb common code to helper functions (v2)")
> 
> I'd drop the Fixes tag completely, as the bug was present in the
> intel and radeon drivers before. But probably it doesn't matter, as no one
> is gonna backport this to v2.6.31 and earlier ;-)
> 
> Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds
> 
> _______________________________________________
> ldv-project mailing list
> ldv-project@linuxtesting.org
> http://linuxtesting.org/cgi-bin/mailman/listinfo/ldv-project
> 

Re: [ldv-project] [PATCH v2] drm/fb-helper: add virtual screen size check to drm_fb_helper_check_var()

[Daniel Vetter]

On Thu, Aug 11, 2022 at 11:59:00PM +0300, Alexey Khoroshilov wrote:
> For v2 I would suggest to update description to something like this:
> 
> Make sure that virtual screen size is not less than physical screen one.
> 
> and comment to:
>     /* make sure that virtual resolution >= physical resolution */

Did this land somewhere? If not please resend with r-b tags and
everything.

Thanks, Daniel

> 
> --
> Alexey
> 
> 
> On 11.08.2022 17:54, Geert Uytterhoeven wrote:
> > Hi Andrey,
> > 
> > On Thu, Aug 11, 2022 at 4:49 PM Andrey Strachuk <strochuk@ispras.ru> wrote:
> >> Add virtual screen size check to drm_fb_helper_check_var() in
> >> order to validate userspace input.
> >>
> >> Found by Linux Verification Center (linuxtesting.org) with syzkaller.
> >>
> >> Signed-off-by: Andrey Strachuk <strochuk@ispras.ru>
> > 
> > Thanks for the update!
> > 
> >> Fixes: 785b93ef8c30 ("drm/kms: move driver specific fb common code to helper functions (v2)")
> > 
> > I'd drop the Fixes tag completely, as the bug was present in the
> > intel and radeon drivers before. But probably it doesn't matter, as no one
> > is gonna backport this to v2.6.31 and earlier ;-)
> > 
> > Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
> > 
> > Gr{oetje,eeting}s,
> > 
> >                         Geert
> > 
> > --
> > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> > 
> > In personal conversations with technical people, I call myself a hacker. But
> > when I'm talking to journalists I just say "programmer" or something like that.
> >                                 -- Linus Torvalds
> > 
> > _______________________________________________
> > ldv-project mailing list
> > ldv-project@linuxtesting.org
> > http://linuxtesting.org/cgi-bin/mailman/listinfo/ldv-project
> > 
> 

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [PATCH v2] drm/fb-helper: add virtual screen size check to drm_fb_helper_check_var()

[Alexey Khoroshilov]

On 06.09.2022 22:54, Daniel Vetter wrote:
> On Thu, Aug 11, 2022 at 11:59:00PM +0300, Alexey Khoroshilov wrote:
>> For v2 I would suggest to update description to something like this:
>>
>> Make sure that virtual screen size is not less than physical screen one.
>>
>> and comment to:
>>     /* make sure that virtual resolution >= physical resolution */
> Did this land somewhere?
As far as I can see it is not.

>  If not please resend with r-b tags and
> everything.
The final version (v3) was resent Fri, 12 Aug 2022 04:32:12 -0700:

https://www.mail-archive.com/dri-devel@lists.freedesktop.org/msg407965.html

--
Alexey