diff options
| author | Ilya Leoshkevich <iii@linux.ibm.com> | 2024-06-21 13:34:57 +0200 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2024-07-03 19:30:22 -0700 |
| commit | f416817197e102b9bc6118101c3be652dac01a44 (patch) | |
| tree | 08e262b45f80c8a00c80369cd4b982cd29d68fb0 /mm/slub.c | |
| parent | 1fdb3c7006d9914e4b070f7eee98dfbdf743ee16 (diff) | |
kmsan: support SLAB_POISON
Avoid false KMSAN negatives with SLUB_DEBUG by allowing kmsan_slab_free()
to poison the freed memory, and by preventing init_object() from
unpoisoning new allocations by using __memset().
There are two alternatives to this approach. First, init_object() can be
marked with __no_sanitize_memory. This annotation should be used with
great care, because it drops all instrumentation from the function, and
any shadow writes will be lost. Even though this is not a concern with
the current init_object() implementation, this may change in the future.
Second, kmsan_poison_memory() calls may be added after memset() calls.
The downside is that init_object() is called from free_debug_processing(),
in which case poisoning will erase the distinction between simply
uninitialized memory and UAF.
Link: https://lkml.kernel.org/r/20240621113706.315500-14-iii@linux.ibm.com
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Alexander Potapenko <glider@google.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: <kasan-dev@googlegroups.com>
Cc: Marco Elver <elver@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Steven Rostedt (Google) <rostedt@goodmis.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/slub.c')
| -rw-r--r-- | mm/slub.c | 15 |
1 files changed, 11 insertions, 4 deletions
diff --git a/mm/slub.c b/mm/slub.c index 4927edec6a8c..dbe8a6303937 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -1139,7 +1139,13 @@ static void init_object(struct kmem_cache *s, void *object, u8 val) unsigned int poison_size = s->object_size; if (s->flags & SLAB_RED_ZONE) { - memset(p - s->red_left_pad, val, s->red_left_pad); + /* + * Here and below, avoid overwriting the KMSAN shadow. Keeping + * the shadow makes it possible to distinguish uninit-value + * from use-after-free. + */ + memset_no_sanitize_memory(p - s->red_left_pad, val, + s->red_left_pad); if (slub_debug_orig_size(s) && val == SLUB_RED_ACTIVE) { /* @@ -1152,12 +1158,13 @@ static void init_object(struct kmem_cache *s, void *object, u8 val) } if (s->flags & __OBJECT_POISON) { - memset(p, POISON_FREE, poison_size - 1); - p[poison_size - 1] = POISON_END; + memset_no_sanitize_memory(p, POISON_FREE, poison_size - 1); + memset_no_sanitize_memory(p + poison_size - 1, POISON_END, 1); } if (s->flags & SLAB_RED_ZONE) - memset(p + poison_size, val, s->inuse - poison_size); + memset_no_sanitize_memory(p + poison_size, val, + s->inuse - poison_size); } static void restore_bytes(struct kmem_cache *s, char *message, u8 data, |