diff options
authorQian Cai <cai@lca.pw>2020-08-14 17:31:14 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2020-08-14 19:56:56 -0700
commit69d0b54d41f915ae45afed6669d34a305cf95ff3 (patch)
parent88db0aa2421666d2f73486d15b239a4521983d55 (diff)
mm/kmemleak: silence KCSAN splats in checksum
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> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Acked-by: Marco Elver <elver@google.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Link: http://lkml.kernel.org/r/20200317182754.2180-1-cai@lca.pw Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 files changed, 2 insertions, 0 deletions
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;
+ kcsan_disable_current();
object->checksum = crc32(0, (void *)object->pointer, object->size);
+ kcsan_enable_current();
return object->checksum != old_csum;