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Commit ed18adc1 authored by Kees Cook's avatar Kees Cook
Browse files

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: default avatarKees Cook <keescook@chromium.org>
Tested-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Reviwed-by: default avatarLaura Abbott <labbott@redhat.com>
parent 04385fc5

init/Kconfig

+1 −0
Original line number Diff line number Diff line
@@ -1766,6 +1766,7 @@ 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).

mm/slub.c

+40 −0
Original line number Diff line number Diff line
@@ -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;