kasan: make tag based mode work with CONFIG_HARDENED_USERCOPY

xairy · torvalds · commit 96fedce27e13 · 2019-01-08T17:15:11.000-08:00
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>
diff --git a/mm/slub.c b/mm/slub.c
@@ -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;
 
