KCSAN: data-race in __process_echoes / n_tty

KCSAN: data-race in __process_echoes / n_tty_write (5)
Status: auto-closed as invalid on 2021/11/04 02:47
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 112d, last: 112d

similar bugs (4):
Kernel	Title	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in __process_echoes / n_tty_write	3	522d	563d	0/22	auto-closed as invalid on 2020/09/20 17:41
upstream	KCSAN: data-race in __process_echoes / n_tty_write (3)	7	235d	300d	0/22	auto-closed as invalid on 2021/07/04 10:36
upstream	KCSAN: data-race in __process_echoes / n_tty_write (4)	1	193d	193d	0/22	auto-closed as invalid on 2021/08/15 21:06
upstream	KCSAN: data-race in __process_echoes / n_tty_write (2)	4	390d	409d	0/22	auto-closed as invalid on 2021/01/30 23:25

Sample crash report:

==================================================================
BUG: KCSAN: data-race in __process_echoes / n_tty_write

write to 0xffffc90004afb278 of 8 bytes by task 1131 on cpu 0:
 __process_echoes+0x607/0x660 drivers/tty/n_tty.c:765
 flush_echoes drivers/tty/n_tty.c:826 [inline]
 __receive_buf drivers/tty/n_tty.c:1579 [inline]
 n_tty_receive_buf_common+0x4c38/0x4e70 drivers/tty/n_tty.c:1674
 n_tty_receive_buf2+0x2e/0x40 drivers/tty/n_tty.c:1709
 tty_ldisc_receive_buf+0x5b/0xf0 drivers/tty/tty_buffer.c:471
 tty_port_default_receive_buf+0x54/0x80 drivers/tty/tty_port.c:39
 receive_buf drivers/tty/tty_buffer.c:491 [inline]
 flush_to_ldisc+0x1c5/0x2c0 drivers/tty/tty_buffer.c:543
 process_one_work+0x402/0x910 kernel/workqueue.c:2297
 worker_thread+0x636/0xae0 kernel/workqueue.c:2444
 kthread+0x262/0x280 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30

read to 0xffffc90004afb278 of 8 bytes by task 14736 on cpu 1:
 process_echoes drivers/tty/n_tty.c:803 [inline]
 n_tty_write+0x148/0xaf0 drivers/tty/n_tty.c:2274
 do_tty_write drivers/tty/tty_io.c:1038 [inline]
 file_tty_write+0x409/0x660 drivers/tty/tty_io.c:1110
 tty_write+0x24/0x30 drivers/tty/tty_io.c:1131
 call_write_iter include/linux/fs.h:2163 [inline]
 do_iter_readv_writev+0x2de/0x380 fs/read_write.c:729
 do_iter_write+0x192/0x5c0 fs/read_write.c:855
 vfs_writev fs/read_write.c:928 [inline]
 do_writev+0x210/0x440 fs/read_write.c:971
 __do_sys_writev fs/read_write.c:1044 [inline]
 __se_sys_writev fs/read_write.c:1041 [inline]
 __x64_sys_writev+0x41/0x50 fs/read_write.c:1041
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x000000000000016e -> 0x0000000000000174

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 14736 Comm: syz-executor.1 Not tainted 5.15.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================

Crashes (1):
Manager	Time	Kernel	Commit	Syzkaller	Config	Log	Report	Syz repro	C repro	VM info	Title
ci2-upstream-kcsan-gce	2021/09/30 02:40	upstream	02d5e016800d	be530f6c	.config	log	report			info	KCSAN: data-race in __process_echoes / n_tty_write