The patch titled Subject: kfence: skip all GFP_ZONEMASK allocations has been added to the -mm tree. Its filename is kfence-skip-all-gfp_zonemask-allocations.patch

This patch should soon appear at https://ozlabs.org/~akpm/mmots/broken-out/kfence-skip-all-gfp_zonemask-alloc... and later at https://ozlabs.org/~akpm/mmotm/broken-out/kfence-skip-all-gfp_zonemask-alloc...

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------------------------------------------------------ From: Alexander Potapenko glider@google.com Subject: 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: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") Signed-off-by: Alexander Potapenko glider@google.com Reviewed-by: Marco Elver elver@google.com Acked-by: Souptick 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: Andrew Morton akpm@linux-foundation.org ---

mm/kfence/core.c | 9 +++++++++ 1 file changed, 9 insertions(+)

--- a/mm/kfence/core.c~kfence-skip-all-gfp_zonemask-allocations +++ a/mm/kfence/core.c @@ -741,6 +741,15 @@ void *__kfence_alloc(struct kmem_cache * 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 * cost, in case we have a large number of concurrent allocations. _

Patches currently in -mm which might be from glider@google.com are

kfence-move-the-size-check-to-the-beginning-of-__kfence_alloc.patch kfence-skip-all-gfp_zonemask-allocations.patch