From: Qian Cai <cai@lca.pw>
To: akpm@linux-foundation.org
Cc: elver@google.com, catalin.marinas@arm.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Qian Cai <cai@lca.pw>
Subject: [PATCH] mm/kmemleak: silence KCSAN splats in checksum
Date: Tue, 17 Mar 2020 14:27:54 -0400 [thread overview]
Message-ID: <20200317182754.2180-1-cai@lca.pw> (raw)
Even if KCSAN is disabled for kmemleak, update_checksum() could still
call crc32() (which is outside of kmemleak.c) to dereference
object->pointer. Thus, the value of object->pointer could be accessed
concurrently as noticed by KCSAN,
BUG: KCSAN: data-race in crc32_le_base / do_raw_spin_lock
write to 0xffffb0ea683a7d50 of 4 bytes by task 23575 on cpu 12:
do_raw_spin_lock+0x114/0x200
debug_spin_lock_after at kernel/locking/spinlock_debug.c:91
(inlined by) do_raw_spin_lock at kernel/locking/spinlock_debug.c:115
_raw_spin_lock+0x40/0x50
__handle_mm_fault+0xa9e/0xd00
handle_mm_fault+0xfc/0x2f0
do_page_fault+0x263/0x6f9
page_fault+0x34/0x40
read to 0xffffb0ea683a7d50 of 4 bytes by task 839 on cpu 60:
crc32_le_base+0x67/0x350
crc32_le_base+0x67/0x350:
crc32_body at lib/crc32.c:106
(inlined by) crc32_le_generic at lib/crc32.c:179
(inlined by) crc32_le at lib/crc32.c:197
kmemleak_scan+0x528/0xd90
update_checksum at mm/kmemleak.c:1172
(inlined by) kmemleak_scan at mm/kmemleak.c:1497
kmemleak_scan_thread+0xcc/0xfa
kthread+0x1e0/0x200
ret_from_fork+0x27/0x50
If a shattered value was returned due to a data race, it will be
corrected in the next scan. Thus, let KCSAN ignore all reads in the
region to silence KCSAN in case the write side is non-atomic.
Suggested-by: Marco Elver <elver@google.com>
Signed-off-by: Qian Cai <cai@lca.pw>
---
mm/kmemleak.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/mm/kmemleak.c b/mm/kmemleak.c
index e362dc3d2028..5e252d91eb14 100644
--- a/mm/kmemleak.c
+++ b/mm/kmemleak.c
@@ -1169,8 +1169,10 @@ static bool update_checksum(struct kmemleak_object *object)
u32 old_csum = object->checksum;
kasan_disable_current();
+ kcsan_disable_current();
object->checksum = crc32(0, (void *)object->pointer, object->size);
kasan_enable_current();
+ kcsan_enable_current();
return object->checksum != old_csum;
}
--
2.21.0 (Apple Git-122.2)
next reply other threads:[~2020-03-17 18:28 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-17 18:27 Qian Cai [this message]
2020-03-17 18:41 ` [PATCH] mm/kmemleak: silence KCSAN splats in checksum Marco Elver
2020-03-18 8:51 ` Catalin Marinas
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