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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>
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@ -1766,6 +1766,7 @@ config SLAB
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config SLUB
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bool "SLUB (Unqueued Allocator)"
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select HAVE_HARDENED_USERCOPY_ALLOCATOR
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help
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SLUB is a slab allocator that minimizes cache line usage
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instead of managing queues of cached objects (SLAB approach).
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40
mm/slub.c
40
mm/slub.c
@ -3614,6 +3614,46 @@ void *__kmalloc_node(size_t size, gfp_t flags, int node)
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EXPORT_SYMBOL(__kmalloc_node);
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#endif
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#ifdef CONFIG_HARDENED_USERCOPY
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/*
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* Rejects objects that are incorrectly sized.
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*
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* Returns NULL if check passes, otherwise const char * to name of cache
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* to indicate an error.
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*/
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const char *__check_heap_object(const void *ptr, unsigned long n,
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struct page *page)
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{
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struct kmem_cache *s;
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unsigned long offset;
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size_t object_size;
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/* Find object and usable object size. */
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s = page->slab_cache;
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object_size = slab_ksize(s);
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/* Reject impossible pointers. */
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if (ptr < page_address(page))
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return s->name;
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/* Find offset within object. */
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offset = (ptr - page_address(page)) % s->size;
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/* Adjust for redzone and reject if within the redzone. */
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if (kmem_cache_debug(s) && s->flags & SLAB_RED_ZONE) {
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if (offset < s->red_left_pad)
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return s->name;
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offset -= s->red_left_pad;
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}
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/* Allow address range falling entirely within object size. */
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if (offset <= object_size && n <= object_size - offset)
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return NULL;
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return s->name;
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}
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#endif /* CONFIG_HARDENED_USERCOPY */
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static size_t __ksize(const void *object)
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{
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struct page *page;
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