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 <[email protected]>
Cc: Andrey Ryabinin <[email protected]>
Cc: Christoph Lameter <[email protected]>
Cc: Dmitry Vyukov <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Vincenzo Frascino <[email protected]>
Cc: Will Deacon <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/mm/slub.c b/mm/slub.c
index 36c0befeebd8083187f6b869f1aa975d23ee6651..1e3d0ec4e2007b6c68fdc92d1cff5e5eebd3d266 100644 (file)
--- 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;