On Wed, Jun 30, 2021 at 8:32 PM Alexander Potapenko glider@google.com wrote:
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).
Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure") Cc: Andrew Morton akpm@linux-foundation.org Cc: Dmitry Vyukov dvyukov@google.com Cc: Marco Elver elver@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: Alexander Potapenko glider@google.com Reviewed-by: Marco Elver elver@google.com
v2:
- added parentheses around the GFP clause, as requested by Marco
v3:
- ignore GFP_ZONEMASK, which also covers __GFP_HIGHMEM and __GFP_MOVABLE
- move the flag check at the beginning of the function, as requested by Souptick Joarder
Acked-by: Souptick Joarder jrdr.linux@gmail.com
v4:
- minor fixes to description and comment formatting
mm/kfence/core.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/mm/kfence/core.c b/mm/kfence/core.c index 33bb20d91bf6a..1cbdb62e6d0fb 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -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-- 2.32.0.93.g670b81a890-goog