Commit 236e9f15 authored by Alexander Potapenko's avatar Alexander Potapenko Committed by Linus Torvalds
Browse files

kfence: skip all GFP_ZONEMASK allocations 

Allocation requests outside ZONE_NORMAL (MOVABLE, HIGHMEM or DMA) cannot
be fulfilled by KFENCE, because KFENCE memory pool is located in a zone
different from the requested one.

Because callers of kmem_cache_alloc() may actually rely on the
allocation to reside in the requested zone (e.g.  memory allocations
done with __GFP_DMA must be DMAable), skip all allocations done with
GFP_ZONEMASK and/or respective SLAB flags (SLAB_CACHE_DMA and
SLAB_CACHE_DMA32).

Link: https://lkml.kernel.org/r/20210714092222.1890268-2-glider@google.com


Fixes: 0ce20dd8 ("mm: add Kernel Electric-Fence infrastructure")
Signed-off-by: default avatarAlexander Potapenko <glider@google.com>
Reviewed-by: default avatarMarco Elver <elver@google.com>
Acked-by: default avatarSouptick Joarder <jrdr.linux@gmail.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Souptick Joarder <jrdr.linux@gmail.com>
Cc: <stable@vger.kernel.org>	[5.12+]
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 235a85cb

mm/kfence/core.c

+9 −0
Original line number Diff line number Diff line
@@ -740,6 +740,15 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags) 
	if (size > PAGE_SIZE)

		return NULL;



	/*

	 * Skip allocations from non-default zones, including DMA. We cannot

	 * guarantee that pages in the KFENCE pool will have the requested

	 * properties (e.g. reside in DMAable memory).

	 */

	if ((flags & GFP_ZONEMASK) ||

	    (s->flags & (SLAB_CACHE_DMA | SLAB_CACHE_DMA32)))

		return NULL;



	/*

	 * allocation_gate only needs to become non-zero, so it doesn't make

	 * sense to continue writing to it and pay the associated contention