linux-kernel - Re: [PATCH] drm/amdgpu: Fix possible NULL pointer dereference

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Message-ID: <de0e660b-395f-4a26-8bbc-199df83a90b4@amd.com>
Date: Mon, 28 Oct 2024 20:03:31 +0530
From: "Lazar, Lijo" <lijo.lazar@....com>
To: Li Huafei <lihuafei1@...wei.com>, alexander.deucher@....com
Cc: christian.koenig@....com, Xinhui.Pan@....com, airlied@...il.com,
 simona@...ll.ch, Hawking.Zhang@....com, yifan1.zhang@....com,
 Likun.Gao@....com, Tim.Huang@....com, pratap.nirujogi@....com,
 victorchengchi.lu@....com, Jun.Ma2@....com, le.ma@....com,
 amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/amdgpu: Fix possible NULL pointer dereference



On 10/29/2024 3:29 AM, Li Huafei wrote:
> Fix the potential NULL pointer dereference on mem_ranges in
> amdgpu_discovery_get_nps_info(). Additionally, assign the output
> parameters nps_type and range_cnt after the kvzalloc() call to prevent
> modifying the output parameters in case of an error return.
> 
> Fixes: b194d21b9bcc ("drm/amdgpu: Use NPS ranges from discovery table")
> Signed-off-by: Li Huafei <lihuafei1@...wei.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
> index 4bd61c169ca8..1b1aedebb3c2 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_discovery.c
> @@ -1757,11 +1757,13 @@ int amdgpu_discovery_get_nps_info(struct amdgpu_device *adev,
>  
>  	switch (le16_to_cpu(nps_info->v1.header.version_major)) {
>  	case 1:
> -		*nps_type = nps_info->v1.nps_type;
> -		*range_cnt = nps_info->v1.count;

This one is used in the allocation call below. If you prefer to not
assign any of the out params before memory allocation is successful,
then use nps_info->v1.count in the alloc call.

Thanks for adding the alloc fail check.

Thanks,
Lijo
>  		mem_ranges = kvzalloc(
>  			*range_cnt * sizeof(struct amdgpu_gmc_memrange),
>  			GFP_KERNEL);
> +		if (!mem_ranges)
> +			return -ENOMEM;
> +		*nps_type = nps_info->v1.nps_type;
> +		*range_cnt = nps_info->v1.count;
>  		for (i = 0; i < *range_cnt; i++) {
>  			mem_ranges[i].base_address =
>  				nps_info->v1.instance_info[i].base_address;