diff options
author | Kees Cook <keescook@chromium.org> | 2016-06-23 15:24:05 -0700 |
---|---|---|
committer | Alex Shi <alex.shi@linaro.org> | 2016-08-27 11:23:38 +0800 |
commit | 3ad78bad4fd43467f1fc6dff63076789b30c116b (patch) | |
tree | 486b0bde0d21734f1a3ba5a52803e6204f128074 | |
parent | 784bd0f8d7303ff0025e2ea44b68b6fc6323544d (diff) |
mm: SLUB hardened usercopy support
Under CONFIG_HARDENED_USERCOPY, this adds object size checking to the
SLUB allocator to catch any copies that may span objects. Includes a
redzone handling fix discovered by Michael Ellerman.
Based on code from PaX and grsecurity.
Signed-off-by: Kees Cook <keescook@chromium.org>
Tested-by: Michael Ellerman <mpe@ellerman.id.au>
Reviwed-by: Laura Abbott <labbott@redhat.com>
(cherry picked from commit ed18adc1cdd00a5c55a20fbdaed4804660772281)
Signed-off-by: Alex Shi <alex.shi@linaro.org>
-rw-r--r-- | init/Kconfig | 1 | ||||
-rw-r--r-- | mm/slub.c | 40 |
2 files changed, 41 insertions, 0 deletions
diff --git a/init/Kconfig b/init/Kconfig index fa031a140397..e1d1d6936f92 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -1727,6 +1727,7 @@ config SLAB config SLUB bool "SLUB (Unqueued Allocator)" + select HAVE_HARDENED_USERCOPY_ALLOCATOR help SLUB is a slab allocator that minimizes cache line usage instead of managing queues of cached objects (SLAB approach). diff --git a/mm/slub.c b/mm/slub.c index 65d5f92d51d2..fbadb3753d4d 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3585,6 +3585,46 @@ void *__kmalloc_node(size_t size, gfp_t flags, int node) EXPORT_SYMBOL(__kmalloc_node); #endif +#ifdef CONFIG_HARDENED_USERCOPY +/* + * Rejects objects that are incorrectly sized. + * + * Returns NULL if check passes, otherwise const char * to name of cache + * to indicate an error. + */ +const char *__check_heap_object(const void *ptr, unsigned long n, + struct page *page) +{ + struct kmem_cache *s; + unsigned long offset; + size_t object_size; + + /* Find object and usable object size. */ + s = page->slab_cache; + object_size = slab_ksize(s); + + /* Reject impossible pointers. */ + if (ptr < page_address(page)) + return s->name; + + /* Find offset within object. */ + offset = (ptr - page_address(page)) % s->size; + + /* Adjust for redzone and reject if within the redzone. */ + if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE) { + if (offset < s->red_left_pad) + return s->name; + offset -= s->red_left_pad; + } + + /* Allow address range falling entirely within object size. */ + if (offset <= object_size && n <= object_size - offset) + return NULL; + + return s->name; +} +#endif /* CONFIG_HARDENED_USERCOPY */ + static size_t __ksize(const void *object) { struct page *page; |