KCSAN: data-race in n_tty_write / tty_set

KCSAN: data-race in n_tty_write / tty_set_termios (3)
Status: auto-closed as invalid on 2020/12/02 18:50
Reported-by: syzbot+@syzkaller.appspotmail.com
First crash: 327d, last: 327d

similar bugs (4):
Kernel	Title	Count	Last	Reported	Patched	Status
upstream	KCSAN: data-race in n_tty_write / tty_set_termios (4)	3	236d	286d	0/22	auto-closed as invalid on 2021/03/04 08:49
upstream	KCSAN: data-race in n_tty_write / tty_set_termios (2)	1	392d	392d	0/22	auto-closed as invalid on 2020/09/29 07:57
upstream	KCSAN: data-race in n_tty_write / tty_set_termios (5)	2	125d	127d	0/22	auto-closed as invalid on 2021/06/22 15:42
upstream	KCSAN: data-race in n_tty_write / tty_set_termios	1	454d	454d	0/22	auto-closed as invalid on 2020/07/29 04:13

Sample crash report:

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

read-write to 0xffff8881012d111c of 4 bytes by task 8158 on cpu 0:
 unset_locked_termios drivers/tty/tty_ioctl.c:254 [inline]
 tty_set_termios+0x1a3/0x870 drivers/tty/tty_ioctl.c:331
 set_termios+0x352/0x380 drivers/tty/tty_ioctl.c:414
 tty_mode_ioctl+0x644/0x7d0 drivers/tty/tty_ioctl.c:770
 n_tty_ioctl_helper+0x8b/0x460 drivers/tty/tty_ioctl.c:940
 n_tty_ioctl+0x102/0x200 drivers/tty/n_tty.c:2466
 tty_ioctl+0xa5b/0xfd0 drivers/tty/tty_io.c:2663
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:739
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:739
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881012d111c of 4 bytes by task 18672 on cpu 1:
 n_tty_write+0x86/0xae0 drivers/tty/n_tty.c:2310
 do_tty_write drivers/tty/tty_io.c:962 [inline]
 tty_write+0x3fc/0x5e0 drivers/tty/tty_io.c:1046
 vfs_write+0x1b9/0x690 fs/read_write.c:603
 ksys_write+0xce/0x180 fs/read_write.c:658
 __do_sys_write fs/read_write.c:670 [inline]
 __se_sys_write fs/read_write.c:667 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:667
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 18672 Comm: syz-executor.1 Not tainted 5.10.0-rc1-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	2020/10/28 18:42	upstream	ed8780e3f2ec	f24824d3	.config	log	report			info