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. _
