syzbot


INFO: task hung in sb_start_write

Status: upstream: reported on 2024/07/26 04:36
Reported-by: syzbot+a73460915482a2c3b3c7@syzkaller.appspotmail.com
First crash: 43d, last: 43d
Similar bugs (2)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in sb_start_write ext4 401 1h09m 44d 0/27 upstream: reported on 2024/07/25 06:18
linux-6.1 INFO: task hung in sb_start_write 4 41d 51d 0/3 upstream: reported on 2024/07/18 10:36

Sample crash report:
INFO: task syz.0.580:6546 blocked for more than 143 seconds.
      Not tainted 5.15.163-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.580       state:D stack:28512 pid: 6546 ppid:  3570 flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5030 [inline]
 __schedule+0x12c4/0x45b0 kernel/sched/core.c:6376
 schedule+0x11b/0x1f0 kernel/sched/core.c:6459
 percpu_rwsem_wait+0x3e1/0x470 kernel/locking/percpu-rwsem.c:160
 __percpu_down_read+0xd0/0x100 kernel/locking/percpu-rwsem.c:174
 percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
 __sb_start_write include/linux/fs.h:1811 [inline]
 sb_start_write+0x182/0x1c0 include/linux/fs.h:1881
 mnt_want_write+0x3b/0x80 fs/namespace.c:377
 filename_create+0x180/0x530 fs/namei.c:3828
 do_mkdirat+0xb3/0x520 fs/namei.c:4080
 __do_sys_mkdirat fs/namei.c:4105 [inline]
 __se_sys_mkdirat fs/namei.c:4103 [inline]
 __x64_sys_mkdirat+0x85/0x90 fs/namei.c:4103
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fa8d3c2c299
RSP: 002b:00007fa8d2069048 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007fa8d3dbb130 RCX: 00007fa8d3c2c299
RDX: 00000000000001ff RSI: 0000000020001080 RDI: 0000000000000008
RBP: 00007fa8d3c998e6 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007fa8d3dbb130 R15: 00007ffd7f49fd18
 </TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/27:
 #0: ffffffff8c91fb20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
2 locks held by kworker/u4:1/144:
2 locks held by getty/3328:
 #0: ffff88814b606098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
 #1: ffffc90002bab2e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6af/0x1db0 drivers/tty/n_tty.c:2158
2 locks held by kworker/1:3/3559:
 #0: ffff888011c72138 ((wq_completion)rcu_gp){+.+.}-{0:0}, at: process_one_work+0x78a/0x10c0 kernel/workqueue.c:2283
 #1: ffffc90002c37d20 ((work_completion)(&rew.rew_work)){+.+.}-{0:0}, at: process_one_work+0x7d0/0x10c0 kernel/workqueue.c:2285
1 lock held by udevd/3560:
 #0: ffff88801b43a918 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_get_by_dev+0x14d/0xa50 block/bdev.c:817
4 locks held by kworker/u4:5/3649:
3 locks held by kworker/1:15/4536:
 #0: ffff888022e29538 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work+0x78a/0x10c0 kernel/workqueue.c:2283
 #1: ffffc90003047d20 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work+0x7d0/0x10c0 kernel/workqueue.c:2285
 #2: ffffffff8da30848 (rtnl_mutex){+.+.}-{3:3}, at: addrconf_dad_work+0xcc/0x1720 net/ipv6/addrconf.c:4112
3 locks held by kworker/1:20/4757:
 #0: ffff888011c70938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x78a/0x10c0 kernel/workqueue.c:2283
 #1: ffffc9000328fd20 ((work_completion)(&data->fib_event_work)){+.+.}-{0:0}, at: process_one_work+0x7d0/0x10c0 kernel/workqueue.c:2285
 #2: ffff88801b3ff240 (&data->fib_lock){+.+.}-{3:3}, at: nsim_fib_event_work+0x2cd/0x4120 drivers/net/netdevsim/fib.c:1478
1 lock held by udevd/4826:
 #0: ffffffff8c9240e8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:290 [inline]
 #0: ffffffff8c9240e8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x280/0x740 kernel/rcu/tree_exp.h:845
1 lock held by syz.0.580/6546:
 #0: ffff888079d8a460 (sb_writers#5){++++}-{0:0}, at: mnt_want_write+0x3b/0x80 fs/namespace.c:377
4 locks held by syz-executor/8881:
 #0: ffffffff8da30848 (rtnl_mutex){+.+.}-{3:3}, at: rtnl_lock net/core/rtnetlink.c:72 [inline]
 #0: ffffffff8da30848 (rtnl_mutex){+.+.}-{3:3}, at: rtnetlink_rcv_msg+0x94c/0xee0 net/core/rtnetlink.c:5626
 #1: ffffffff8c91fb20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x5/0x30 include/linux/rcupdate.h:311
 #2: ffff8880b9a3a358 (&rq->__lock){-.-.}-{2:2}, at: raw_spin_rq_lock_nested+0x26/0x140 kernel/sched/core.c:475
 #3: ffffffff8c91fb20 (rcu_read_lock){....}-{1:2}, at: psi_task_switch+0x149/0x810 kernel/sched/psi.c:857
1 lock held by syz.3.1076/9064:
 #0: ffffffff8c9240e8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:322 [inline]
 #0: ffffffff8c9240e8 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x350/0x740 kernel/rcu/tree_exp.h:845
2 locks held by syz.2.1080/9077:
 #0: ffff88801b43a918 (&disk->open_mutex){+.+.}-{3:3}, at: blkdev_put+0xfb/0x790 block/bdev.c:912
 #1: ffff888147859468 (&lo->lo_mutex){+.+.}-{3:3}, at: lo_release+0x4d/0x1f0 drivers/block/loop.c:2070

=============================================

NMI backtrace for cpu 1
CPU: 1 PID: 27 Comm: khungtaskd Not tainted 5.15.163-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
 nmi_cpu_backtrace+0x46a/0x4a0 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x181/0x2a0 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:210 [inline]
 watchdog+0xe72/0xeb0 kernel/hung_task.c:295
 kthread+0x3f6/0x4f0 kernel/kthread.c:334
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 PID: 8881 Comm: syz-executor Not tainted 5.15.163-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 06/27/2024
RIP: 0010:usage_skip kernel/locking/lockdep.c:2237 [inline]
RIP: 0010:__bfs kernel/locking/lockdep.c:1745 [inline]
RIP: 0010:__bfs_backwards kernel/locking/lockdep.c:1805 [inline]
RIP: 0010:check_irq_usage kernel/locking/lockdep.c:2745 [inline]
RIP: 0010:check_prev_add kernel/locking/lockdep.c:3057 [inline]
RIP: 0010:check_prevs_add kernel/locking/lockdep.c:3172 [inline]
RIP: 0010:validate_chain+0x1b96/0x5930 kernel/locking/lockdep.c:3788
Code: 4d 8b 3e 49 8d 9f ba 00 00 00 48 89 d8 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df 0f b6 04 08 84 c0 0f 85 81 02 00 00 80 3b 01 <0f> 85 98 00 00 00 48 b8 00 00 00 00 00 fc ff df 48 8b 4c 24 58 0f
RSP: 0018:ffffc900031b6c40 EFLAGS: 00000097
RAX: 0000000000000000 RBX: ffffffff8f9c013a RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffc900031b6d60
RBP: ffffc900031b6ef0 R08: dffffc0000000000 R09: fffffbfff1f8e01c
R10: 0000000000000000 R11: dffffc0000000001 R12: ffffffff90dd66f8
R13: 000000000004aedc R14: ffffffff90dd6708 R15: ffffffff8f9c0080
FS:  0000555556e68500(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000001b31810ff8 CR3: 000000005c668000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <NMI>
 </NMI>
 <TASK>
 __lock_acquire+0x1295/0x1ff0 kernel/locking/lockdep.c:5012
 lock_acquire+0x1db/0x4f0 kernel/locking/lockdep.c:5623
 __raw_spin_lock include/linux/spinlock_api_smp.h:142 [inline]
 _raw_spin_lock+0x2a/0x40 kernel/locking/spinlock.c:154
 spin_lock include/linux/spinlock.h:363 [inline]
 d_walk+0x6e/0x6c0 fs/dcache.c:1340
 shrink_dcache_parent+0x142/0x480 fs/dcache.c:1605
 d_invalidate+0x118/0x2d0 fs/dcache.c:1717
 simple_recursive_removal+0x3a7/0x850 fs/libfs.c:290
 debugfs_remove+0x45/0x60 fs/debugfs/inode.c:745
 ieee80211_debugfs_remove_netdev+0x4d/0xa0 net/mac80211/debugfs_netdev.c:851
 ieee80211_teardown_sdata net/mac80211/iface.c:687 [inline]
 ieee80211_if_change_type+0x162/0x9f0 net/mac80211/iface.c:1744
 ieee80211_change_iface+0x57/0x430 net/mac80211/cfg.c:160
 rdev_change_virtual_intf net/wireless/rdev-ops.h:69 [inline]
 cfg80211_change_iface+0x789/0xf20 net/wireless/util.c:1074
 nl80211_set_interface+0x5f7/0x890 net/wireless/nl80211.c:3949
 genl_family_rcv_msg_doit net/netlink/genetlink.c:731 [inline]
 genl_family_rcv_msg net/netlink/genetlink.c:775 [inline]
 genl_rcv_msg+0xfbd/0x14a0 net/netlink/genetlink.c:792
 netlink_rcv_skb+0x1cf/0x410 net/netlink/af_netlink.c:2504
 genl_rcv+0x24/0x40 net/netlink/genetlink.c:803
 netlink_unicast_kernel net/netlink/af_netlink.c:1326 [inline]
 netlink_unicast+0x7b6/0x980 net/netlink/af_netlink.c:1352
 netlink_sendmsg+0xa30/0xd60 net/netlink/af_netlink.c:1920
 sock_sendmsg_nosec net/socket.c:704 [inline]
 __sock_sendmsg net/socket.c:716 [inline]
 __sys_sendto+0x564/0x720 net/socket.c:2058
 __do_sys_sendto net/socket.c:2070 [inline]
 __se_sys_sendto net/socket.c:2066 [inline]
 __x64_sys_sendto+0xda/0xf0 net/socket.c:2066
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f1067f2a02c
Code: 2a 5a 02 00 44 8b 4c 24 2c 4c 8b 44 24 20 89 c5 44 8b 54 24 28 48 8b 54 24 18 b8 2c 00 00 00 48 8b 74 24 10 8b 7c 24 08 0f 05 <48> 3d 00 f0 ff ff 77 34 89 ef 48 89 44 24 08 e8 70 5a 02 00 48 8b
RSP: 002b:00007ffc4b2fb9e0 EFLAGS: 00000293 ORIG_RAX: 000000000000002c
RAX: ffffffffffffffda RBX: 00007f1068be5620 RCX: 00007f1067f2a02c
RDX: 0000000000000024 RSI: 00007f1068be5670 RDI: 0000000000000003
RBP: 0000000000000000 R08: 00007ffc4b2fba34 R09: 000000000000000c
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000003
R13: 0000000000000000 R14: 00007f1068be5670 R15: 0000000000000000
 </TASK>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2024/07/26 04:35 linux-5.15.y 7c6d66f0266f 3f86dfed .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan INFO: task hung in sb_start_write
* Struck through repros no longer work on HEAD.