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

[Maíra Canal]

Hi Alexander,

On 28/05/26 15:54, Alexander A. Klimov wrote:
> On 5/28/26 20:17, Maíra Canal wrote:
> > 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.
>
> Strange...
> It comes already directly after num_uniforms, doesn't it?

Yeah, it does. However, usually, we declare the variables and then we
proceed to the functions. Check, for example, the function
record_texture_sample() in vc4.

Best regards,
- Maíra

> At least when I apply my patch to Linus' master.