Check the allocation size before toggling kfence_allocation_gate. This way allocations that can't be served by KFENCE will not result in waiting for another CONFIG_KFENCE_SAMPLE_INTERVAL without allocating anything.
Suggested-by: Marco Elver elver@google.com 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: stable@vger.kernel.org # 5.12+ Signed-off-by: Alexander Potapenko glider@google.com Reviewed-by: Marco Elver elver@google.com --- mm/kfence/core.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-)
diff --git a/mm/kfence/core.c b/mm/kfence/core.c index d7666ace9d2e4..2623ff401a104 100644 --- a/mm/kfence/core.c +++ b/mm/kfence/core.c @@ -733,6 +733,13 @@ void kfence_shutdown_cache(struct kmem_cache *s)
void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags) { + /* + * Perform size check before switching kfence_allocation_gate, so that + * we don't disable KFENCE without making an allocation. + */ + if (size > PAGE_SIZE) + 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 @@ -757,9 +764,6 @@ void *__kfence_alloc(struct kmem_cache *s, size_t size, gfp_t flags) if (!READ_ONCE(kfence_enabled)) return NULL;
- if (size > PAGE_SIZE) - return NULL; - return kfence_guarded_alloc(s, size, flags); }
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 Acked-by: Souptick Joarder jrdr.linux@gmail.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 v4: - minor fixes to description and comment formatting v5: - pick Acked-by:, rebase --- mm/kfence/core.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/mm/kfence/core.c b/mm/kfence/core.c index 2623ff401a104..575c685aa6422 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
linux-stable-mirror@lists.linaro.org
-
Alexander Potapenko