Re: [PATCH v2] drm/amdgpu: fix integer overflow in amdgpu_gem_align_pitch()

[Christian König]

On 4/14/26 07:08, Werner Kasselman wrote:
> amdgpu_gem_align_pitch() is passed u32 width and cpp from dumb buffer
> creation but uses signed int internally.  The round-up add and the
> aligned * cpp multiplication can overflow, returning zero or a negative
> pitch.  A zero pitch propagates to a zero-sized GEM object allocation
> that reaches userspace via DRM_IOCTL_MODE_CREATE_DUMB.
> 
> Switch the helper to unsigned int and use check_add_overflow() /
> check_mul_overflow() so wraparound returns zero.  Reject a zero pitch
> or size in amdgpu_mode_dumb_create() rather than allocating a zero-
> byte BO.
> 
> Fixes: 8e911ab770f7 ("drm: amdgpu: Replace drm_fb_get_bpp_depth() with drm_format_plane_cpp()")
> Cc: stable@xxxxxxxxxxxxxxx

The patch looks valid to me, but I think we can drop this CC: stable.

Since dump buffers are a kernel only interface the fix has no practical relevance and is only of cosmetic nature.

Regards,
Christian.

> Signed-off-by: Werner Kasselman <werner@xxxxxxxxxxx>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 25 +++++++++++++++++--------
>  1 file changed, 17 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> index a6107109a2b8..0d9309f792a4 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
> @@ -27,6 +27,7 @@
>   */
>  #include <linux/ktime.h>
>  #include <linux/module.h>
> +#include <linux/overflow.h>
>  #include <linux/pagemap.h>
>  #include <linux/pci.h>
>  #include <linux/dma-buf.h>
> @@ -1223,13 +1224,14 @@ int amdgpu_gem_list_handles_ioctl(struct drm_device *dev, void *data,
>  	return ret;
>  }
>  
> -static int amdgpu_gem_align_pitch(struct amdgpu_device *adev,
> -				  int width,
> -				  int cpp,
> -				  bool tiled)
> +static unsigned int amdgpu_gem_align_pitch(struct amdgpu_device *adev,
> +					   unsigned int width,
> +					   unsigned int cpp,
> +					   bool tiled)
>  {
> -	int aligned = width;
> -	int pitch_mask = 0;
> +	unsigned int aligned = width;
> +	unsigned int pitch_mask = 0;
> +	unsigned int pitch;
>  
>  	switch (cpp) {
>  	case 1:
> @@ -1244,9 +1246,12 @@ static int amdgpu_gem_align_pitch(struct amdgpu_device *adev,
>  		break;
>  	}
>  
> -	aligned += pitch_mask;
> +	if (check_add_overflow(aligned, pitch_mask, &aligned))
> +		return 0;
>  	aligned &= ~pitch_mask;
> -	return aligned * cpp;
> +	if (check_mul_overflow(aligned, cpp, &pitch))
> +		return 0;
> +	return pitch;
>  }
>  
>  int amdgpu_mode_dumb_create(struct drm_file *file_priv,
> @@ -1273,8 +1278,12 @@ int amdgpu_mode_dumb_create(struct drm_file *file_priv,
>  
>  	args->pitch = amdgpu_gem_align_pitch(adev, args->width,
>  					     DIV_ROUND_UP(args->bpp, 8), 0);
> +	if (!args->pitch)
> +		return -EINVAL;
>  	args->size = (u64)args->pitch * args->height;
>  	args->size = ALIGN(args->size, PAGE_SIZE);
> +	if (!args->size)
> +		return -EINVAL;
>  	domain = amdgpu_bo_get_preferred_domain(adev,
>  				amdgpu_display_supported_domains(adev, flags));
>  	r = amdgpu_gem_object_create(adev, args->size, 0, domain, flags,