Commit 96fedce2 authored Jan 08, 2019 by Andrey Konovalov Committed by Linus Torvalds Jan 08, 2019

kasan: make tag based mode work with CONFIG_HARDENED_USERCOPY

With CONFIG_HARDENED_USERCOPY enabled __check_heap_object() compares and
then subtracts a potentially tagged pointer with a non-tagged address of
the page that this pointer belongs to, which leads to unexpected
behavior.

Untag the pointer in __check_heap_object() before doing any of these
operations.

Link: http://lkml.kernel.org/r/7e756a298d514c4482f52aea6151db34818d395d.1546540962.git.andreyknvl@google.com


Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Cc: Andrey Ryabinin <aryabinin@virtuozzo.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Vincenzo Frascino <vincenzo.frascino@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent eb214f2d

mm/slub.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -3846,6 +3846,8 @@ void __check_heap_object(const void ptr, unsigned long n, struct page page,
		unsigned int offset;
		size_t object_size;

		ptr = kasan_reset_tag(ptr);

		/* Find object and usable object size. */
		s = page->slab_cache;

Admin message