| From 235a85cb32bb123854ad31de46fdbf04c1d57cda Mon Sep 17 00:00:00 2001 |
| From: Alexander Potapenko <glider@google.com> |
| Date: Fri, 23 Jul 2021 15:50:11 -0700 |
| Subject: kfence: move the size check to the beginning of __kfence_alloc() |
| |
| From: Alexander Potapenko <glider@google.com> |
| |
| commit 235a85cb32bb123854ad31de46fdbf04c1d57cda upstream. |
| |
| 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 <glider@google.com> |
| Suggested-by: Marco Elver <elver@google.com> |
| Reviewed-by: Marco Elver <elver@google.com> |
| 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: Andrew Morton <akpm@linux-foundation.org> |
| Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
| Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| --- |
| mm/kfence/core.c | 10 +++++++--- |
| 1 file changed, 7 insertions(+), 3 deletions(-) |
| |
| --- a/mm/kfence/core.c |
| +++ b/mm/kfence/core.c |
| @@ -734,6 +734,13 @@ void kfence_shutdown_cache(struct kmem_c |
| 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 |
| * cost, in case we have a large number of concurrent allocations. |
| @@ -757,9 +764,6 @@ void *__kfence_alloc(struct kmem_cache * |
| if (!READ_ONCE(kfence_enabled)) |
| return NULL; |
| |
| - if (size > PAGE_SIZE) |
| - return NULL; |
| - |
| return kfence_guarded_alloc(s, size, flags); |
| } |
| |