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KCSAN: data-race in __process_echoes / n_tty_write (12)

Status: moderation: reported on 2024/06/11 14:33
Subsystems: serial
[Documentation on labels]
Reported-by: syzbot+9e60a0f30774a95b26aa@syzkaller.appspotmail.com
First crash: 6d22h, last: 1d05h
Similar bugs (11)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KCSAN: data-race in __process_echoes / n_tty_write (9) serial 4 337d 383d 0/27 auto-obsoleted due to no activity on 2023/08/21 10:01
upstream KCSAN: data-race in __process_echoes / n_tty_write serial 3 1401d 1443d 0/27 auto-closed as invalid on 2020/09/20 17:41
upstream KCSAN: data-race in __process_echoes / n_tty_write (3) serial 7 1115d 1180d 0/27 auto-closed as invalid on 2021/07/04 10:36
upstream KCSAN: data-race in __process_echoes / n_tty_write (11) serial 13 67d 146d 0/27 auto-obsoleted due to no activity on 2024/05/16 20:06
upstream KCSAN: data-race in __process_echoes / n_tty_write (10) serial 10 191d 191d 0/27 auto-obsoleted due to no activity on 2024/01/14 04:02
upstream KCSAN: data-race in __process_echoes / n_tty_write (4) serial 1 1072d 1072d 0/27 auto-closed as invalid on 2021/08/15 21:06
upstream KCSAN: data-race in __process_echoes / n_tty_write (6) serial 41 623d 919d 0/27 auto-obsoleted due to no activity on 2022/11/07 20:53
upstream KCSAN: data-race in __process_echoes / n_tty_write (2) serial 4 1269d 1289d 0/27 auto-closed as invalid on 2021/01/30 23:25
upstream KCSAN: data-race in __process_echoes / n_tty_write (7) serial 2 567d 568d 0/27 auto-obsoleted due to no activity on 2023/01/13 20:09
upstream KCSAN: data-race in __process_echoes / n_tty_write (5) serial 1 992d 992d 0/27 auto-closed as invalid on 2021/11/04 02:47
upstream KCSAN: data-race in __process_echoes / n_tty_write (8) serial 3 430d 483d 0/27 auto-obsoleted due to no activity on 2023/05/19 15:46

Sample crash report:
==================================================================
BUG: KCSAN: data-race in __process_echoes / n_tty_write

write to 0xffffc90000eb5280 of 8 bytes by task 50 on cpu 1:
 __process_echoes+0x688/0x6b0 drivers/tty/n_tty.c:746
 flush_echoes drivers/tty/n_tty.c:807 [inline]
 __receive_buf drivers/tty/n_tty.c:1642 [inline]
 n_tty_receive_buf_common+0x8f9/0xbe0 drivers/tty/n_tty.c:1739
 n_tty_receive_buf2+0x33/0x40 drivers/tty/n_tty.c:1785
 tty_ldisc_receive_buf+0x63/0x100 drivers/tty/tty_buffer.c:387
 tty_port_default_receive_buf+0x59/0x90 drivers/tty/tty_port.c:37
 receive_buf drivers/tty/tty_buffer.c:445 [inline]
 flush_to_ldisc+0x1ce/0x410 drivers/tty/tty_buffer.c:495
 process_one_work kernel/workqueue.c:3231 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3312
 worker_thread+0x526/0x730 kernel/workqueue.c:3393
 kthread+0x1d1/0x210 kernel/kthread.c:389
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffffc90000eb5280 of 8 bytes by task 22819 on cpu 0:
 process_echoes drivers/tty/n_tty.c:784 [inline]
 n_tty_write+0x172/0xb90 drivers/tty/n_tty.c:2375
 iterate_tty_write drivers/tty/tty_io.c:1021 [inline]
 file_tty_write+0x386/0x690 drivers/tty/tty_io.c:1096
 tty_write+0x28/0x30 drivers/tty/tty_io.c:1117
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0x78f/0x900 fs/read_write.c:590
 ksys_write+0xeb/0x1b0 fs/read_write.c:643
 __do_sys_write fs/read_write.c:655 [inline]
 __se_sys_write fs/read_write.c:652 [inline]
 __x64_sys_write+0x42/0x50 fs/read_write.c:652
 x64_sys_call+0x27ef/0x2d70 arch/x86/include/generated/asm/syscalls_64.h:2
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000004 -> 0x0000000000000008

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 22819 Comm: syz-executor.4 Tainted: G        W          6.10.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/07/2024
==================================================================

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/06/17 07:46 upstream 6ba59ff42279 f429ab00 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __process_echoes / n_tty_write
2024/06/11 14:33 upstream 83a7eefedc9b b7d9eb04 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-kcsan-gce KCSAN: data-race in __process_echoes / n_tty_write
* Struck through repros no longer work on HEAD.