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

["Lazar, Lijo" <lijo.lazar@amd.com>]

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@huawei.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;