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

[Maíra Canal]

Hi Alexander,

LGTM, but a small styling nit:

On 26/05/26 15:41, 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;
>
> Fixes: 6d45c81d229d ("drm/vc4: Add support for branching in shader validation.")
> Signed-off-by: Alexander A. Klimov <grandmaster@xxxxxxxxxxxx>
> ---
>   drivers/gpu/drm/vc4/vc4_validate_shaders.c | 12 ++++++------
>   1 file changed, 6 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..af48758592f9 100644
> --- a/drivers/gpu/drm/vc4/vc4_validate_shaders.c
> +++ b/drivers/gpu/drm/vc4/vc4_validate_shaders.c
> @@ -291,14 +291,14 @@ 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;

Declare the variable here.

>   
> -	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)
> +	void *mem = krealloc(validated_shader->uniform_addr_offsets,

Instead of void *, you should probably use uint32_t *.

Best regards,
- Maíra

> +			     (o + 1) *
> +			     sizeof(*validated_shader->uniform_addr_offsets),
> +			     GFP_KERNEL);
> +	if (!mem)
>   		return false;
>   
> +	validated_shader->uniform_addr_offsets = mem;
>   	validated_shader->uniform_addr_offsets[o] = num_uniforms;
>   	validated_shader->num_uniform_addr_offsets++;
>