From 235a85cb32bb123854ad31de46fdbf04c1d57cda Mon Sep 17 00:00:00 2001 From: Alexander Potapenko Date: Fri, 23 Jul 2021 15:50:11 -0700 Subject: [PATCH] kfence: move the size check to the beginning of __kfence_alloc() 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. Link: https://lkml.kernel.org/r/20210714092222.1890268-1-glider@google.com Signed-off-by: Alexander Potapenko Suggested-by: Marco Elver Reviewed-by: Marco Elver Cc: Dmitry Vyukov Cc: Marco Elver Cc: Greg Kroah-Hartman Cc: [5.12+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- 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 d7666ace9d2e..2623ff401a10 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); }