Re: [PATCH] media: exynos4-is: fix DMA memory double free

[Marek Szyprowski <m.szyprowski@samsung.com>]

On 27.10.2026 15:53, Guangshuo Li wrote:
> fimc_is_alloc_cpu_memory() frees the coherent DMA buffer when its
> DMA address does not satisfy the firmware alignment requirement,
> but leaves is->memory.vaddr non-NULL.
>
> Because firmware loading is asynchronous, this error path may run
> after probe has returned successfully. A later remove can then
> attempt to free the same DMA allocation again.
>
> Set is->memory.vaddr to NULL after freeing the buffer so the
> existing NULL check in fimc_is_free_cpu_memory() skips the
> already-freed allocation.
>
> This issue was found by our static analysis tool under development.
>
> Fixes: db47622c13ae ("media: platform: exynos4-is: remove all references to physical addresses")
> Cc: stable@vger.kernel.org
> Signed-off-by: Guangshuo Li <lgs201920130244@gmail.com>

Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>

but I would relax a bit the severity of this issue. I'm not sure if it
makes sense to bother stable team with it and I would add 'potential'
word to the subject. In practice this case would not happen.


> ---
>  drivers/media/platform/samsung/exynos4-is/fimc-is.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/drivers/media/platform/samsung/exynos4-is/fimc-is.c b/drivers/media/platform/samsung/exynos4-is/fimc-is.c
> index b7d9bfedd590..9fdc352abfe4 100644
> --- a/drivers/media/platform/samsung/exynos4-is/fimc-is.c
> +++ b/drivers/media/platform/samsung/exynos4-is/fimc-is.c
> @@ -346,6 +346,7 @@ static int fimc_is_alloc_cpu_memory(struct fimc_is *is)
>  			(u32)is->memory.addr);
>  		dma_free_coherent(dev, is->memory.size, is->memory.vaddr,
>  				  is->memory.addr);
> +		is->memory.vaddr = NULL;
>  		return -EIO;
>  	}
>  

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland