syzbot


INFO: task hung in bfs_lookup

Status: upstream: reported C repro on 2025/02/28 02:48
Reported-by: syzbot+329c4002dad0055b432b@syzkaller.appspotmail.com
First crash: 12d, last: 12d
Bug presence (1)
Date Name Commit Repro Result
2025/02/28 upstream (ToT) 76544811c850 C Failed due to an error; will retry later
Similar bugs (5)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in bfs_lookup (4) bfs 1 241d 241d 0/28 auto-obsoleted due to no activity on 2024/10/11 22:29
linux-4.19 INFO: task hung in bfs_lookup 1 825d 825d 0/1 auto-obsoleted due to no activity on 2023/04/07 07:53
upstream INFO: task hung in bfs_lookup bfs 1 694d 694d 0/28 auto-obsoleted due to no activity on 2023/07/17 03:03
upstream INFO: task hung in bfs_lookup (3) bfs 20 312d 325d 0/28 auto-obsoleted due to no activity on 2024/06/22 13:07
upstream INFO: task hung in bfs_lookup (2) bfs 2 505d 549d 0/28 auto-obsoleted due to no activity on 2024/01/21 21:34

Sample crash report:
INFO: task syz-executor185:4296 blocked for more than 143 seconds.
      Not tainted 6.1.129-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor185 state:D stack:0     pid:4296  ppid:4292   flags:0x0000000d
Call trace:
 __switch_to+0x308/0x598 arch/arm64/kernel/process.c:553
 context_switch kernel/sched/core.c:5243 [inline]
 __schedule+0xef4/0x1d44 kernel/sched/core.c:6560
 schedule+0xc4/0x170 kernel/sched/core.c:6636
 schedule_preempt_disabled+0x18/0x2c kernel/sched/core.c:6695
 __mutex_lock_common+0xbd8/0x21a0 kernel/locking/mutex.c:679
 __mutex_lock kernel/locking/mutex.c:747 [inline]
 mutex_lock_nested+0x38/0x44 kernel/locking/mutex.c:799
 bfs_lookup+0x11c/0x228 fs/bfs/dir.c:136
 __lookup_slow+0x250/0x374 fs/namei.c:1690
 lookup_slow+0x60/0x84 fs/namei.c:1707
 walk_component fs/namei.c:1998 [inline]
 link_path_walk+0x830/0xcc8 fs/namei.c:2325
 path_parentat fs/namei.c:2526 [inline]
 __filename_parentat+0x1e4/0x5d0 fs/namei.c:2550
 filename_parentat fs/namei.c:2568 [inline]
 filename_create+0xf0/0x468 fs/namei.c:3857
 do_mkdirat+0xac/0x510 fs/namei.c:4121
 __do_sys_mkdirat fs/namei.c:4146 [inline]
 __se_sys_mkdirat fs/namei.c:4144 [inline]
 __arm64_sys_mkdirat+0x90/0xa8 fs/namei.c:4144
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x2bc arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x138/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x58/0x13c arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x168 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
 #0: ffff800015cc79b0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x44/0xcf4 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
 #0: ffff800015cc81b0 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x44/0xcf4 kernel/rcu/tasks.h:517
1 lock held by khungtaskd/28:
 #0: ffff800015cc77e0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0xc/0x44 include/linux/rcupdate.h:349
2 locks held by getty/4054:
 #0: ffff0000d5f76098 (&tty->ldisc_sem){++++}-{0:0}, at: ldsem_down_read+0x3c/0x4c drivers/tty/tty_ldsem.c:340
 #1: ffff80001d8f02f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x414/0x1214 drivers/tty/n_tty.c:2198
3 locks held by syz-executor185/4294:
2 locks held by syz-executor185/4296:
 #0: ffff0000e1b4c168 (&type->i_mutex_dir_key#8){.+.+}-{3:3}, at: inode_lock_shared include/linux/fs.h:768 [inline]
 #0: ffff0000e1b4c168 (&type->i_mutex_dir_key#8){.+.+}-{3:3}, at: lookup_slow+0x50/0x84 fs/namei.c:1706
 #1: ffff0000c316d8d8 (&info->bfs_lock){+.+.}-{3:3}, at: bfs_lookup+0x11c/0x228 fs/bfs/dir.c:136

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Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/02/28 02:47 linux-6.1.y 3a8358583626 6a8fcbc4 .config console log report syz / log C [disk image] [vmlinux] [kernel image] [mounted in repro] ci2-linux-6-1-kasan-arm64 INFO: task hung in bfs_lookup
* Struck through repros no longer work on HEAD.