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

From: "Ville Syrjälä" <ville.syrjala@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>
Cc: intel-gfx@lists.freedesktop.org, stable@vger.kernel.org
Subject: Re: [Intel-gfx] [PATCH] drm/i915/gem: Detect overflow in calculating dumb buffer size
Date: Thu, 23 Jan 2020 15:27:07 +0200	[thread overview]
Message-ID: <20200123132707.GK13686@intel.com> (raw)
In-Reply-To: <20200123125934.1401755-1-chris@chris-wilson.co.uk>

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@chris-wilson.co.uk>
> Cc: Ramalingam C <ramalingam.c@intel.com>
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Cc: stable@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?

>  
>  	mem_type = INTEL_MEMORY_SYSTEM;
>  	if (HAS_LMEM(to_i915(dev)))
> -- 
> 2.25.0
> 
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-- 
Ville Syrjälä
Intel