The patch titled Subject: kasan: fix type cast in memory_is_poisoned_n has been added to the -mm mm-hotfixes-unstable branch. Its filename is kasan-fix-type-cast-in-memory_is_poisoned_n.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Andrey Konovalov andreyknvl@google.com Subject: kasan: fix type cast in memory_is_poisoned_n Date: Tue, 4 Jul 2023 02:52:05 +0200

Commit bb6e04a173f0 ("kasan: use internal prototypes matching gcc-13 builtins") introduced a bug into the memory_is_poisoned_n implementation: it effectively removed the cast to a signed integer type after applying KASAN_GRANULE_MASK.

As a result, KASAN started failing to properly check memset, memcpy, and other similar functions.

Fix the bug by adding the cast back (through an additional signed integer variable to make the code more readable).

Link: https://lkml.kernel.org/r/8c9e0251c2b8b81016255709d4ec42942dcaf018.168843186... Fixes: bb6e04a173f0 ("kasan: use internal prototypes matching gcc-13 builtins") Signed-off-by: Andrey Konovalov andreyknvl@google.com Cc: Alexander Potapenko glider@google.com Cc: Andrey Ryabinin ryabinin.a.a@gmail.com Cc: Arnd Bergmann arnd@arndb.de Cc: Dmitry Vyukov dvyukov@google.com Cc: Marco Elver elver@google.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

mm/kasan/generic.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/mm/kasan/generic.c~kasan-fix-type-cast-in-memory_is_poisoned_n +++ a/mm/kasan/generic.c @@ -130,9 +130,10 @@ static __always_inline bool memory_is_po if (unlikely(ret)) { const void *last_byte = addr + size - 1; s8 *last_shadow = (s8 *)kasan_mem_to_shadow(last_byte); + s8 last_accessible_byte = (unsigned long)last_byte & KASAN_GRANULE_MASK;

if (unlikely(ret != (unsigned long)last_shadow || - (((long)last_byte & KASAN_GRANULE_MASK) >= *last_shadow))) + last_accessible_byte >= *last_shadow)) return true; } return false; _

Patches currently in -mm which might be from andreyknvl@google.com are

kasan-fix-type-cast-in-memory_is_poisoned_n.patch