linux-kernel - Re: [PATCH v2] amdgpu: prevent NULL pointer dereference if ATIF is not supported

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Message-ID: <00e9b1f0-7bc1-418c-8e67-e8f1893be665@amd.com>
Date: Thu, 31 Oct 2024 14:37:19 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: Antonio Quartulli <antonio@...delbit.com>, alexander.deucher@....com,
 christian.koenig@....com, Xinhui.Pan@....com
Cc: amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] amdgpu: prevent NULL pointer dereference if ATIF is
 not supported

On 10/31/2024 10:28, Antonio Quartulli wrote:
> acpi_evaluate_object() may return AE_NOT_FOUND (failure), which
> would result in dereferencing buffer.pointer (obj) while being NULL.
> 
> Although this case may be unrealistic for the current code, it is
> still better to protect against possible bugs.
> 
> Bail out also when status is AE_NOT_FOUND.
> 
> This fixes 1 FORWARD_NULL issue reported by Coverity
> Report: CID 1600951:  Null pointer dereferences  (FORWARD_NULL)
> 
> Signed-off-by: Antonio Quartulli <antonio@...delbit.com>

Can you please dig up the right Fixes: tag?

Besides that, LGTM.

Reviewed-by: Mario Limonciello <mario.limonciello@....com>

> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> index cce85389427f..b8d4e07d2043 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_acpi.c
> @@ -172,8 +172,8 @@ static union acpi_object *amdgpu_atif_call(struct amdgpu_atif *atif,
>   				      &buffer);
>   	obj = (union acpi_object *)buffer.pointer;
>   
> -	/* Fail if calling the method fails and ATIF is supported */
> -	if (ACPI_FAILURE(status) && status != AE_NOT_FOUND) {
> +	/* Fail if calling the method fails */
> +	if (ACPI_FAILURE(status)) {
>   		DRM_DEBUG_DRIVER("failed to evaluate ATIF got %s\n",
>   				 acpi_format_exception(status));
>   		kfree(obj);