Re: [PATCH v4 2/2] kfence: skip all GFP_ZONEMASK allocations
From: Souptick Joarder <hidden>
Date: 2021-07-05 18:39:03
Also in:
lkml, stable
On Wed, Jun 30, 2021 at 8:32 PM Alexander Potapenko [off-list ref] 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 <redacted>
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 JoarderAcked-by: Souptick Joarder <redacted>
quoted hunk ↗ jump to hunk
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