linux-kernel - Re: [PATCH-next v2] Fix unintentional integer overflow

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Message-ID: <1dbd3687-ab21-421e-a978-3fdd8597046c@amd.com>
Date: Fri, 4 Oct 2024 16:49:36 +0530
From: "Lazar, Lijo" <lijo.lazar@....com>
To: Advait Dhamorikar <advaitdhamorikar@...il.com>,
 alexander.deucher@....com, christian.koenig@....com, Xinhui.Pan@....com,
 airlied@...il.com, simona@...ll.ch, leo.liu@....com,
 sathishkumar.sundararaju@....com, saleemkhan.jamadar@....com,
 Veerabadhran.Gopalakrishnan@....com, sonny.jiang@....com
Cc: amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, skhan@...uxfoundation.org,
 anupnewsmail@...il.com
Subject: Re: [PATCH-next v2] Fix unintentional integer overflow



On 10/3/2024 3:56 PM, Advait Dhamorikar wrote:
> Fix shift-count-overflow in JPEG instance
> multiplication. The expression's value may not be
> what the programmer intended, because the expression
> is evaluated using a narrower integer type.
> 
> Fixes: f0b19b84d391 ("drm/amdgpu: add amdgpu_jpeg_sched_mask debugfs")
> Signed-off-by: Advait Dhamorikar <advaitdhamorikar@...il.com>
> ---
>  V1 -> V2: addressed review comments
>  
>  drivers/gpu/drm/amd/amdgpu/amdgpu_jpeg.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_jpeg.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_jpeg.c
> index 95e2796919fc..b6f0435f56ba 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_jpeg.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_jpeg.c
> @@ -357,7 +357,7 @@ static int amdgpu_debugfs_jpeg_sched_mask_set(void *data, u64 val)
>  	if (!adev)
>  		return -ENODEV;
>  
> -	mask = (1 << (adev->jpeg.num_jpeg_inst * adev->jpeg.num_jpeg_rings)) - 1;
> +	mask = ((uint64_t)1 << (adev->jpeg.num_jpeg_inst * adev->jpeg.num_jpeg_rings)) - 1;

Using 1ULL here is more legible.

Thanks,
Lijo

>  	if ((val & mask) == 0)
>  		return -EINVAL;
>