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author | Kees Cook <keescook@chromium.org> | 2016-06-23 15:24:05 -0700 |
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committer | Kees Cook <keescook@chromium.org> | 2016-07-26 14:43:54 -0700 |
commit | ed18adc1cdd00a5c55a20fbdaed4804660772281 (patch) | |
tree | 652ad77b2d5e9ed24eb4782c2b270c7e7b4fc0c1 /mm | |
parent | 04385fc5e8fffed84425d909a783c0f0c587d847 (diff) | |
download | linux-stable-ed18adc1cdd00a5c55a20fbdaed4804660772281.tar.gz linux-stable-ed18adc1cdd00a5c55a20fbdaed4804660772281.tar.bz2 linux-stable-ed18adc1cdd00a5c55a20fbdaed4804660772281.zip |
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>
Diffstat (limited to 'mm')
-rw-r--r-- | mm/slub.c | 40 |
1 files changed, 40 insertions, 0 deletions
diff --git a/mm/slub.c b/mm/slub.c index 825ff4505336..256a8efd165e 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3614,6 +3614,46 @@ 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; |