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-allocations.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/kfence-skip-all-gfp_zonemask-allocations.patch
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------------------------------------------------------
From: Alexander Potapenko <glider@xxxxxxxxxx>
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@xxxxxxxxxx
Fixes: 0ce20dd84089 ("mm: add Kernel Electric-Fence infrastructure")
Signed-off-by: Alexander Potapenko <glider@xxxxxxxxxx>
Reviewed-by: Marco Elver <elver@xxxxxxxxxx>
Acked-by: Souptick Joarder <jrdr.linux@xxxxxxxxx>
Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Souptick Joarder <jrdr.linux@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [5.12+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
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@xxxxxxxxxx are
kfence-move-the-size-check-to-the-beginning-of-__kfence_alloc.patch
kfence-skip-all-gfp_zonemask-allocations.patch
