Re: [PATCH mm] kfence: make compatible with kmemleak

[Catalin Marinas <catalin.marinas@arm.com>]

On Wed, Mar 17, 2021 at 09:47:40AM +0100, Marco Elver wrote:
> Because memblock allocations are registered with kmemleak, the KFENCE
> pool was seen by kmemleak as one large object. Later allocations through
> kfence_alloc() that were registered with kmemleak via
> slab_post_alloc_hook() would then overlap and trigger a warning.
> Therefore, once the pool is initialized, we can remove (free) it from
> kmemleak again, since it should be treated as allocator-internal and be
> seen as "free memory".
> 
> The second problem is that kmemleak is passed the rounded size, and not
> the originally requested size, which is also the size of KFENCE objects.
> To avoid kmemleak scanning past the end of an object and trigger a
> KFENCE out-of-bounds error, fix the size if it is a KFENCE object.
> 
> For simplicity, to avoid a call to kfence_ksize() in
> slab_post_alloc_hook() (and avoid new IS_ENABLED(CONFIG_DEBUG_KMEMLEAK)
> guard), just call kfence_ksize() in mm/kmemleak.c:create_object().
> 
> Reported-by: Luis Henriques <lhenriques@suse.de>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Marco Elver <elver@google.com>

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>