The patch titled
Subject: mm/kmemleak: silence KCSAN splats in checksum
has been added to the -mm tree. Its filename is
mm-kmemleak-silence-kcsan-splats-in-checksum.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/mm-kmemleak-silence-kcsan-splats-in-checksum.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/mm-kmemleak-silence-kcsan-splats-in-checksum.patch
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------------------------------------------------------
From: Qian Cai <cai@xxxxxx>
Subject: 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.
Link: http://lkml.kernel.org/r/20200317182754.2180-1-cai@xxxxxx
Signed-off-by: Qian Cai <cai@xxxxxx>
Suggested-by: Marco Elver <elver@xxxxxxxxxx>
Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/kmemleak.c | 2 ++
1 file changed, 2 insertions(+)
--- a/mm/kmemleak.c~mm-kmemleak-silence-kcsan-splats-in-checksum
+++ a/mm/kmemleak.c
@@ -1169,8 +1169,10 @@ static bool update_checksum(struct kmeml
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;
}
_
Patches currently in -mm which might be from cai@xxxxxx are
page-flags-fix-a-crash-at-setpageerrorthp_swap.patch
mm-kmemleak-silence-kcsan-splats-in-checksum.patch
mm-disable-kcsan-for-kmemleak.patch
mm-swapfile-fix-data-races-in-try_to_unuse.patch
kasan-detect-negative-size-in-memory-operation-function-fix.patch
mm-vmscan-fix-data-races-at-kswapd_classzone_idx.patch
percpu_counter-fix-a-data-race-at-vm_committed_as.patch
mm-frontswap-mark-various-intentional-data-races.patch
mm-page_io-mark-various-intentional-data-races.patch
mm-page_io-mark-various-intentional-data-races-v2.patch
mm-swap_state-mark-various-intentional-data-races.patch
mm-swapfile-fix-and-annotate-various-data-races.patch
mm-swapfile-fix-and-annotate-various-data-races-v2.patch
mm-page_counter-fix-various-data-races-at-memsw.patch
mm-memcontrol-fix-a-data-race-in-scan-count.patch
mm-list_lru-fix-a-data-race-in-list_lru_count_one.patch
mm-mempool-fix-a-data-race-in-mempool_free.patch
mm-util-annotate-an-data-race-at-vm_committed_as.patch
mm-rmap-annotate-a-data-race-at-tlb_flush_batched.patch
mm-annotate-a-data-race-in-page_zonenum.patch
mm-swap-annotate-data-races-for-lru_rotate_pvecs.patch
