Re: [PATCH 4/6] drm: Avoid suspicious operations in drm_fb_dma_get_gem_addr()

[Sebastian Brzezinka <sebastian.brzezinka@intel.com>]

Hi Krzysztof

On Mon Sep 8, 2025 at 9:25 AM UTC, Krzysztof Karas wrote:
> There are two unsafe scenarios in that function:
>  1) drm_format_info_block_width/height() may return 0 and cause
> division by 0 down the line. Return early if any of these values
> are 0.
>  2) dma_addr calculations are carried out using 32-bit
> arithmetic, which could cause a truncation of the values
> before they are extended to 64 bits. Cast one of the operands
> to dma_addr_t, so 64-bit arithmetic is used.
>
> Fixes: 8c30eecc6769 ("drm/gem: rename struct drm_gem_dma_object.{paddr => dma_addr}")
> Cc: Danilo Krummrich <dakr@redhat.com>
> Cc: <stable@vger.kernel.org> # v6.1+
> Signed-off-by: Krzysztof Karas <krzysztof.karas@intel.com>
> ---
LGTM it could probably be split into two patches, but the changes are pretty small
and it doesn’t really bother me. drm_format_info_block_h/w can both potentially return 0,
so it's good to verify their return values.

Reviewed-by: Sebastian Brzezinka <sebastian.brzezinka@intel.com>

-- 
Best regards,
Sebastian