Re: [PATCH v3] drm/vc4: fix krealloc() memory leak

[Maíra Canal]

On 06/06/26 09:38, Alexander A. Klimov wrote:
> Don't just overwrite the original pointer passed to krealloc()
> with its return value without checking latter:
>
>      MEM = krealloc(MEM, SZ, GFP);
>
> If krealloc() returns NULL, that erases the pointer
> to the still allocated memory, hence leaks this memory.
> Instead, use a temporary variable, check it's not NULL
> and only then assign it to the original pointer:
>
>      TMP = krealloc(MEM, SZ, GFP);
>      if (!TMP) return;
>      MEM = TMP;
>
> While on it, use krealloc_array().
>
> Fixes: 6d45c81d229d ("drm/vc4: Add support for branching in shader validation.")
> Signed-off-by: Alexander A. Klimov <grandmaster@xxxxxxxxxxxx>

Reviewed-by: Maíra Canal <mcanal@xxxxxxxxxx>

Best regards,
- Maíra

> ---
>   v2: Declare the variable explicitly
>   v2: Instead of void *, use u32 *
>   v2: While on it, enhance variable name
>   v3: Use krealloc_array()
>
>   [✓] scripts/checkpatch.pl --strict
>   [✓] allmodconfig compiled (i686, LLVM)
>   [✓] localyesconfig booted (IBM T43)
>
>   Note to myself: use --in-reply-to=e1edeadb7c161580a5cd5c7e642dc1b28db8ee86.camel@xxxxxxxxxxx
>
>   drivers/gpu/drm/vc4/vc4_validate_shaders.c | 13 +++++++------
>   1 file changed, 7 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/vc4/vc4_validate_shaders.c b/drivers/gpu/drm/vc4/vc4_validate_shaders.c
> index d48cf76983c0..66502a6a4a8e 100644
> --- a/drivers/gpu/drm/vc4/vc4_validate_shaders.c
> +++ b/drivers/gpu/drm/vc4/vc4_validate_shaders.c
> @@ -290,15 +290,16 @@ static bool require_uniform_address_uniform(struct vc4_validated_shader_info *va
>   {
>   	uint32_t o = validated_shader->num_uniform_addr_offsets;
>   	uint32_t num_uniforms = validated_shader->uniforms_size / 4;
> +	u32 *offsets;
>   
> -	validated_shader->uniform_addr_offsets =
> -		krealloc(validated_shader->uniform_addr_offsets,
> -			 (o + 1) *
> -			 sizeof(*validated_shader->uniform_addr_offsets),
> -			 GFP_KERNEL);
> -	if (!validated_shader->uniform_addr_offsets)
> +	offsets = krealloc_array(validated_shader->uniform_addr_offsets,
> +				 o + 1,
> +				 sizeof(*validated_shader->uniform_addr_offsets),
> +				 GFP_KERNEL);
> +	if (!offsets)
>   		return false;
>   
> +	validated_shader->uniform_addr_offsets = offsets;
>   	validated_shader->uniform_addr_offsets[o] = num_uniforms;
>   	validated_shader->num_uniform_addr_offsets++;
>