diff options
| author | Qian Cai <cai@lca.pw> | 2020-04-06 20:10:25 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-04-24 07:59:12 +0200 |
| commit | 9729be90f7b18d9ef191039dae34e232e220429c (patch) | |
| tree | 6a3085c8c16c77ed96b08ff1ffd43b54ced380e4 | |
| parent | cb04d347625c2629643bc8328586d6602e0dab6e (diff) | |
percpu_counter: fix a data race at vm_committed_as
[ Upstream commit 7e2345200262e4a6056580f0231cccdaffc825f3 ]
"vm_committed_as.count" could be accessed concurrently as reported by
KCSAN,
BUG: KCSAN: data-race in __vm_enough_memory / percpu_counter_add_batch
write to 0xffffffff9451c538 of 8 bytes by task 65879 on cpu 35:
percpu_counter_add_batch+0x83/0xd0
percpu_counter_add_batch at lib/percpu_counter.c:91
__vm_enough_memory+0xb9/0x260
dup_mm+0x3a4/0x8f0
copy_process+0x2458/0x3240
_do_fork+0xaa/0x9f0
__do_sys_clone+0x125/0x160
__x64_sys_clone+0x70/0x90
do_syscall_64+0x91/0xb05
entry_SYSCALL_64_after_hwframe+0x49/0xbe
read to 0xffffffff9451c538 of 8 bytes by task 66773 on cpu 19:
__vm_enough_memory+0x199/0x260
percpu_counter_read_positive at include/linux/percpu_counter.h:81
(inlined by) __vm_enough_memory at mm/util.c:839
mmap_region+0x1b2/0xa10
do_mmap+0x45c/0x700
vm_mmap_pgoff+0xc0/0x130
ksys_mmap_pgoff+0x6e/0x300
__x64_sys_mmap+0x33/0x40
do_syscall_64+0x91/0xb05
entry_SYSCALL_64_after_hwframe+0x49/0xbe
The read is outside percpu_counter::lock critical section which results in
a data race. Fix it by adding a READ_ONCE() in
percpu_counter_read_positive() which could also service as the existing
compiler memory barrier.
Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Marco Elver <elver@google.com>
Link: http://lkml.kernel.org/r/1582302724-2804-1-git-send-email-cai@lca.pw
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | include/linux/percpu_counter.h | 4 |
1 files changed, 2 insertions, 2 deletions
diff --git a/include/linux/percpu_counter.h b/include/linux/percpu_counter.h index 84a109449610..b6332cb761a4 100644 --- a/include/linux/percpu_counter.h +++ b/include/linux/percpu_counter.h @@ -76,9 +76,9 @@ static inline s64 percpu_counter_read(struct percpu_counter *fbc) */ static inline s64 percpu_counter_read_positive(struct percpu_counter *fbc) { - s64 ret = fbc->count; + /* Prevent reloads of fbc->count */ + s64 ret = READ_ONCE(fbc->count); - barrier(); /* Prevent reloads of fbc->count */ if (ret >= 0) return ret; return 0; |