KCSAN: data-race in __wb_update_bandwidth / percpu_counter_add

KCSAN: data-race in __wb_update_bandwidth / percpu_counter_add_batch (5)
Status: auto-closed as invalid on 2021/09/04 14:56
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 114d, last: 80d

similar bugs (4):
Kernel	Title	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in __wb_update_bandwidth / percpu_counter_add_batch (3)	2	302d	316d	0/22	auto-closed as invalid on 2021/01/24 22:24
upstream	KCSAN: data-race in __wb_update_bandwidth / percpu_counter_add_batch (4)	6	158d	257d	0/22	auto-closed as invalid on 2021/06/18 08:34
upstream	KCSAN: data-race in __wb_update_bandwidth / percpu_counter_add_batch (2)	3	380d	419d	0/22	auto-closed as invalid on 2020/11/08 10:33
upstream	KCSAN: data-race in __wb_update_bandwidth / percpu_counter_add_batch	9	522d	681d	0/22	closed as invalid on 2020/06/18 14:24

Sample crash report:

==================================================================
BUG: KCSAN: data-race in __wb_update_bandwidth / percpu_counter_add_batch

write to 0xffff888100fa7940 of 8 bytes by task 1914 on cpu 1:
 percpu_counter_add_batch+0x9c/0xd0 lib/percpu_counter.c:91
 __add_wb_stat include/linux/backing-dev.h:70 [inline]
 inc_wb_stat include/linux/backing-dev.h:75 [inline]
 __wb_writeout_inc mm/page-writeback.c:592 [inline]
 test_clear_page_writeback+0x34d/0x560 mm/page-writeback.c:2754
 end_page_writeback+0xd7/0x1b0 mm/filemap.c:1548
 ext4_finish_bio+0x3e2/0x430 fs/ext4/page-io.c:143
 ext4_release_io_end+0x98/0x200 fs/ext4/page-io.c:158
 ext4_end_io_end fs/ext4/page-io.c:192 [inline]
 ext4_do_flush_completed_IO fs/ext4/page-io.c:257 [inline]
 ext4_end_io_rsv_work+0x306/0x360 fs/ext4/page-io.c:271
 process_one_work+0x3e9/0x8f0 kernel/workqueue.c:2276
 worker_thread+0x636/0xae0 kernel/workqueue.c:2422
 kthread+0x262/0x280 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

read to 0xffff888100fa7940 of 8 bytes by task 1897 on cpu 0:
 percpu_counter_read include/linux/percpu_counter.h:72 [inline]
 __wb_update_bandwidth+0x9f/0x480 mm/page-writeback.c:1353
 wb_update_bandwidth+0x4e/0x70 mm/page-writeback.c:1387
 wb_writeback+0x421/0x700 fs/fs-writeback.c:2056
 wb_check_old_data_flush fs/fs-writeback.c:2155 [inline]
 wb_do_writeback+0x461/0x510 fs/fs-writeback.c:2208
 wb_workfn+0xc8/0x520 fs/fs-writeback.c:2237
 process_one_work+0x3e9/0x8f0 kernel/workqueue.c:2276
 worker_thread+0x636/0xae0 kernel/workqueue.c:2422
 kthread+0x262/0x280 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

value changed: 0x0000000000000b90 -> 0x0000000000000ba0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1897 Comm: kworker/u4:6 Not tainted 5.14.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: writeback wb_workfn (flush-8:0)
==================================================================

Crashes (3):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	VM info	Title
ci2-upstream-kcsan-gce	2021/07/31 14:48	upstream	c7d102232649	6c236867	.config	log	report	info	KCSAN: data-race in __wb_update_bandwidth / percpu_counter_add_batch
ci2-upstream-kcsan-gce	2021/07/28 21:49	upstream	4010a528219e	9a4781d4	.config	log	report	info	KCSAN: data-race in __wb_update_bandwidth / percpu_counter_add_batch
ci2-upstream-kcsan-gce	2021/06/27 21:40	upstream	b4b27b9eed8e	9d2ab5df	.config	log	report	info	KCSAN: data-race in __wb_update_bandwidth / percpu_counter_add_batch