Re: [PATCH v2] kasan: Initialize tag to 0xff in __kasan_kmalloc

[Nathan Chancellor]

On Thu, May 02, 2019 at 06:40:52PM +0200, Andrey Konovalov wrote:
> On Thu, May 2, 2019 at 6:31 PM Nathan Chancellor
> <natechancellor@xxxxxxxxx> wrote:
> >
> > When building with -Wuninitialized and CONFIG_KASAN_SW_TAGS unset, Clang
> > warns:
> >
> > mm/kasan/common.c:484:40: warning: variable 'tag' is uninitialized when
> > used here [-Wuninitialized]
> >         kasan_unpoison_shadow(set_tag(object, tag), size);
> >                                               ^~~
> >
> > set_tag ignores tag in this configuration but clang doesn't realize it
> > at this point in its pipeline, as it points to arch_kasan_set_tag as
> > being the point where it is used, which will later be expanded to
> > (void *)(object) without a use of tag. Initialize tag to 0xff, as it
> > removes this warning and doesn't change the meaning of the code.
> >
> > Link: https://github.com/ClangBuiltLinux/linux/issues/465
> > Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
> 
> Reviewed-by: Andrey Konovalov <andreyknvl@xxxxxxxxxx>
> 
> Thanks!
> 

Thanks Andrey! Did anyone else have any other comments or can this be
picked up?

Cheers,
Nathan