Hi Krzysztof,
On Tue, Sep 16, 2025 at 06:33:00AM +0000, 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}")
This doesn't need the Fixes tag as it's a very unlikely thing to
happen.
> Cc: Danilo Krummrich <[email protected]>
> Cc: <[email protected]> # v6.1+
> Reviewed-by: Sebastian Brzezinka <[email protected]>
> Signed-off-by: Krzysztof Karas <[email protected]>
> ---
> drivers/gpu/drm/drm_fb_dma_helper.c | 7 +++++--
> 1 file changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_dma_helper.c
> b/drivers/gpu/drm/drm_fb_dma_helper.c
> index fd71969d2fb1..00aaad648a33 100644
> --- a/drivers/gpu/drm/drm_fb_dma_helper.c
> +++ b/drivers/gpu/drm/drm_fb_dma_helper.c
> @@ -85,6 +85,9 @@ dma_addr_t drm_fb_dma_get_gem_addr(struct drm_framebuffer
> *fb,
> u32 block_start_y;
> u32 num_hblocks;
>
> + if (block_w == 0 || block_h == 0)
> + return 0;
This can't go unnoticed, you make the analyzer happy but you
create bigger issues by silently returning '0'.
If you are really concerned you can place here a BUG_ON or
WARN_ON_ONCE.
Andi
> +
> obj = drm_fb_dma_get_gem_obj(fb, plane);
> if (!obj)
> return 0;
