[Intel-gfx] [PATCH] drm/i915/gem: Detect overflow in calculating dumb buffer size

[Chris Wilson]

Quoting Ville Syrjälä (2020-01-23 13:27:07)
> On Thu, Jan 23, 2020 at 12:59:34PM +0000, Chris Wilson wrote:
> > To multiply 2 u32 numbers to generate a u64 in C requires a bit of
> > forewarning for the compiler.
> > 
> > Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> > Cc: Ramalingam C <ramalingam.c at intel.com>
> > Cc: Joonas Lahtinen <joonas.lahtinen at linux.intel.com>
> > Cc: stable at vger.kernel.org
> > ---
> >  drivers/gpu/drm/i915/i915_gem.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> > index 0a20083321a3..ff79da5657f8 100644
> > --- a/drivers/gpu/drm/i915/i915_gem.c
> > +++ b/drivers/gpu/drm/i915/i915_gem.c
> > @@ -265,7 +265,10 @@ i915_gem_dumb_create(struct drm_file *file,
> >                                                   DRM_FORMAT_MOD_LINEAR))
> >               args->pitch = ALIGN(args->pitch, 4096);
> >  
> > -     args->size = args->pitch * args->height;
> > +     if (args->pitch < args->width)
> > +             return -EINVAL;
> > +
> > +     args->size = mul_u32_u32(args->pitch, args->height);
> 
> I thought something would have checked these against the mode_config
> fb limits already. But can't see code like that anywhere. Maybe we
> should just do that in the core?

While it is in uapi/drm_mode.h, is there any restriction that the dumb
buffer has to be used with a framebuffer? Not that I have a good use
case, just wondering if we need to be so proscriptive.

We create something that is compatible but presume we will need later
validation against HW.
-Chris