[PATCH v4] drm/amdgpu: Fix snprintf buffer size in smu_v14_0_init_microcode

[Lazar, Lijo]

On 4/19/2024 9:14 PM, Srinivasan Shanmugam wrote:
> This commit addresses buffer overflow in the smu_v14_0_init_microcode
> function. The issue was about the snprintf function writing more bytes
> into the fw_name buffer than it can hold.
> 
> The line of code is:
> 
> snprintf(fw_name, sizeof(fw_name), "amdgpu/%s.bin", ucode_prefix);
> 
> Here, snprintf is used to write a formatted string into fw_name. The
> format is "amdgpu/%s.bin", where %s is a placeholder for the string
> ucode_prefix. The sizeof(fw_name) argument tells snprintf the maximum
> number of bytes it can write into fw_name, including the
> null-terminating character. In the original code, fw_name is an array of
> 30 characters.
> 
> The string "amdgpu/%s.bin" could be up to 41 bytes long, which exceeds
> the 30 bytes allocated for fw_name. This is because %s could be replaced
> by ucode_prefix, which can be up to 29 characters long. Adding the 12
> characters from "amdgpu/" and ".bin", the total length could be 41
> characters.
> 
> To address this, the size of ucode_prefix has been reduced to 15
> characters. This ensures that the maximum length of the string written
> into fw_name does not exceed its capacity.
> 
> As smu_13/14 etc. don't follow legacy scheme ie.,
> amdgpu_ucode_legacy_naming
> 
> Fixes the below with gcc W=1:
> drivers/gpu/drm/amd/amdgpu/../pm/swsmu/smu14/smu_v14_0.c: In function ‘smu_v14_0_init_microcode’:
> drivers/gpu/drm/amd/amdgpu/../pm/swsmu/smu14/smu_v14_0.c:80:52: warning: ‘%s’ directive output may be truncated writing up to 29 bytes into a region of size 23 [-Wformat-truncation=]
>    80 |         snprintf(fw_name, sizeof(fw_name), "amdgpu/%s.bin", ucode_prefix);
>       |                                                    ^~       ~~~~~~~~~~~~
> drivers/gpu/drm/amd/amdgpu/../pm/swsmu/smu14/smu_v14_0.c:80:9: note: ‘snprintf’ output between 12 and 41 bytes into a destination of size 30
>    80 |         snprintf(fw_name, sizeof(fw_name), "amdgpu/%s.bin", ucode_prefix);
>       |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Fixes: fe6cd9152464 ("drm/amd/swsmu: add smu14 ip support")
> Cc: Li Ma <li.ma at amd.com>
> Cc: Likun Gao <Likun.Gao at amd.com>
> Cc: Lijo Lazar <lijo.lazar at amd.com>
> Cc: Kenneth Feng <kenneth.feng at amd.com>
> Cc: Alex Deucher <alexander.deucher at amd.com>
> Cc: Christian König <christian.koenig at amd.com>
> Signed-off-by: Srinivasan Shanmugam <srinivasan.shanmugam at amd.com>

Reviewed-by: Lijo Lazar <lijo.lazar at amd.com>

Thanks,
Lijo
> ---
> v4:
>  - Reduced ucode_prefix to 15 instead of fw_name size increasing as
>    smu_13/14 etc. don't follow legacy scheme ie.,
>    amdgpu_ucode_legacy_naming (Lijo) 
> 
>  drivers/gpu/drm/amd/pm/swsmu/smu14/smu_v14_0.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/pm/swsmu/smu14/smu_v14_0.c b/drivers/gpu/drm/amd/pm/swsmu/smu14/smu_v14_0.c
> index 7d2055b9d19f..68b9bf822e8d 100644
> --- a/drivers/gpu/drm/amd/pm/swsmu/smu14/smu_v14_0.c
> +++ b/drivers/gpu/drm/amd/pm/swsmu/smu14/smu_v14_0.c
> @@ -65,7 +65,7 @@ int smu_v14_0_init_microcode(struct smu_context *smu)
>  {
>  	struct amdgpu_device *adev = smu->adev;
>  	char fw_name[30];
> -	char ucode_prefix[30];
> +	char ucode_prefix[15];
>  	int err = 0;
>  	const struct smc_firmware_header_v1_0 *hdr;
>  	const struct common_firmware_header *header;