INFO: task hung in p9_fd_close

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 3ffe1e79 Linux 4.14.138
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11d5351c600000
kernel config: https://syzkaller.appspot.com/x/.config?x=978e269523a888e8
dashboard link: https://syzkaller.appspot.com/bug?extid=4c95c74a88b035133d2c
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1338739a600000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=14bbb66a600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4c95c7...@syzkaller.appspotmail.com

audit: type=1400 audit(1565531902.244:36): avc: denied { map } for
pid=7085 comm="syz-executor056" path="/root/syz-executor056047281"
dev="sda1" ino=1426 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1
INFO: task syz-executor056:7087 blocked for more than 140 seconds.
Not tainted 4.14.138 #34
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor056 D28584 7087 7083 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2807 [inline]
__schedule+0x7b8/0x1cd0 kernel/sched/core.c:3383
schedule+0x92/0x1c0 kernel/sched/core.c:3427
schedule_timeout+0x93b/0xe10 kernel/time/timer.c:1721
do_wait_for_common kernel/sched/completion.c:91 [inline]
__wait_for_common kernel/sched/completion.c:112 [inline]
wait_for_common kernel/sched/completion.c:123 [inline]
wait_for_completion+0x27c/0x420 kernel/sched/completion.c:144
flush_work+0x3eb/0x730 kernel/workqueue.c:2885
__cancel_work_timer+0x2f0/0x480 kernel/workqueue.c:2956
cancel_work_sync+0x18/0x20 kernel/workqueue.c:2992
p9_conn_destroy net/9p/trans_fd.c:873 [inline]
p9_fd_close+0x2ae/0x450 net/9p/trans_fd.c:899
p9_client_create+0x787/0x1120 net/9p/client.c:1095
v9fs_session_init+0x1dc/0x1620 fs/9p/v9fs.c:422
v9fs_mount+0x7d/0x870 fs/9p/vfs_super.c:135
mount_fs+0x97/0x2a1 fs/super.c:1237
vfs_kern_mount.part.0+0x5e/0x3d0 fs/namespace.c:1046
vfs_kern_mount fs/namespace.c:1036 [inline]
do_new_mount fs/namespace.c:2549 [inline]
do_mount+0x417/0x27d0 fs/namespace.c:2879
SYSC_mount fs/namespace.c:3095 [inline]
SyS_mount+0xab/0x120 fs/namespace.c:3072
do_syscall_64+0x1e8/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x445a89
RSP: 002b:00007feb96b55d98 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00000000006dac38 RCX: 0000000000445a89
RDX: 0000000020000040 RSI: 0000000020000000 RDI: 0000000000000000
RBP: 00000000006dac30 R08: 0000000020000140 R09: 0000000000000000
R10: 0000000000000001 R11: 0000000000000246 R12: 00000000006dac3c
R13: 0000000020000700 R14: 00000000004ae0a8 R15: 0000000000000005

Showing all locks held in the system:
2 locks held by kworker/0:1/25:
#0: ("events"){+.+.}, at: [<ffffffff813ce59e>] work_static
include/linux/workqueue.h:199 [inline]
#0: ("events"){+.+.}, at: [<ffffffff813ce59e>] set_work_data
kernel/workqueue.c:619 [inline]
#0: ("events"){+.+.}, at: [<ffffffff813ce59e>]
set_work_pool_and_clear_pending kernel/workqueue.c:646 [inline]
#0: ("events"){+.+.}, at: [<ffffffff813ce59e>]
process_one_work+0x76e/0x1600 kernel/workqueue.c:2085
#1: ((&m->wq)){+.+.}, at: [<ffffffff813ce5db>]
process_one_work+0x7ab/0x1600 kernel/workqueue.c:2089
1 lock held by khungtaskd/1013:
#0: (tasklist_lock){.+.+}, at: [<ffffffff81486078>]
debug_show_all_locks+0x7f/0x21f kernel/locking/lockdep.c:4541
2 locks held by getty/7061:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff861bd5f3>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff8310e626>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by getty/7062:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff861bd5f3>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff8310e626>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by getty/7063:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff861bd5f3>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff8310e626>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by getty/7064:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff861bd5f3>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff8310e626>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by getty/7065:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff861bd5f3>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff8310e626>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by getty/7066:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff861bd5f3>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff8310e626>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156
2 locks held by getty/7067:
#0: (&tty->ldisc_sem){++++}, at: [<ffffffff861bd5f3>]
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:377
#1: (&ldata->atomic_read_lock){+.+.}, at: [<ffffffff8310e626>]
n_tty_read+0x1e6/0x17b0 drivers/tty/n_tty.c:2156

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

NMI backtrace for cpu 0
CPU: 0 PID: 1013 Comm: khungtaskd Not tainted 4.14.138 #34
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x138/0x19c lib/dump_stack.c:53
nmi_cpu_backtrace.cold+0x57/0x94 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x141/0x189 lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_all_cpu_backtrace include/linux/nmi.h:140 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:195 [inline]
watchdog+0x5e7/0xb90 kernel/hung_task.c:274
kthread+0x319/0x430 kernel/kthread.c:232
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:404
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at pc 0xffffffff861be0de


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: a5aa8058 Linux 4.19.67
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11efe81e600000
kernel config: https://syzkaller.appspot.com/x/.config?x=8e5f93d2c874cdab
dashboard link: https://syzkaller.appspot.com/bug?extid=cb1a7299534706f76d88

compiler: gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:

Reported-by: syzbot+cb1a72...@syzkaller.appspotmail.com

BFS-fs: bfs_fill_super(): Last block not available: 1587619
INFO: task syz-executor.2:16977 blocked for more than 140 seconds.
Not tainted 4.19.67 #41

"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

syz-executor.2 D28152 16977 7539 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x866/0x1dc0 kernel/sched/core.c:3474
schedule+0x92/0x1c0 kernel/sched/core.c:3518
schedule_timeout+0x8c8/0xfc0 kernel/time/timer.c:1780
do_wait_for_common kernel/sched/completion.c:83 [inline]
__wait_for_common kernel/sched/completion.c:104 [inline]
wait_for_common kernel/sched/completion.c:115 [inline]
wait_for_completion+0x29c/0x440 kernel/sched/completion.c:136
__flush_work+0x49f/0x870 kernel/workqueue.c:2920
__cancel_work_timer+0x3bf/0x520 kernel/workqueue.c:3007
cancel_work_sync+0x18/0x20 kernel/workqueue.c:3043
p9_conn_destroy net/9p/trans_fd.c:883 [inline]
p9_fd_close+0x329/0x570 net/9p/trans_fd.c:913
p9_client_create+0x98c/0x1400 net/9p/client.c:1083
v9fs_session_init+0x1e7/0x18c0 fs/9p/v9fs.c:421
v9fs_mount+0x7d/0x920 fs/9p/vfs_super.c:135
mount_fs+0xa8/0x31f fs/super.c:1261
vfs_kern_mount.part.0+0x6f/0x410 fs/namespace.c:961
vfs_kern_mount fs/namespace.c:951 [inline]
do_new_mount fs/namespace.c:2469 [inline]
do_mount+0x53e/0x2bc0 fs/namespace.c:2799
ksys_mount+0xdb/0x150 fs/namespace.c:3015
__do_sys_mount fs/namespace.c:3029 [inline]
__se_sys_mount fs/namespace.c:3026 [inline]
__x64_sys_mount+0xbe/0x150 fs/namespace.c:3026
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459829
Code: ff ff c3 c5 f8 77 eb 60 80 3d 3c b0 39 01 01 0f 85 7f fd ff ff 48 83
f8 0c 0f 83 74 fe ff ff 48 8d 75 10 66 f7 c6 f0 0f 0f 84 <66> fd ff ff f3
0f 6f 4d 00 48 8d 74 17 f1 49 c7 c1 10 00 00 00 49
RSP: 002b:00007fc3c2341c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000459829
RDX: 0000000020000100 RSI: 0000000020000140 RDI: 0000000000000000
RBP: 000000000075c118 R08: 00000000200001c0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007fc3c23426d4
R13: 00000000004c5dcf R14: 00000000004da890 R15: 00000000ffffffff

Showing all locks held in the system:

2 locks held by kworker/u4:1/23:
#0: 0000000011891ec1 (&rq->lock){-.-.}, at: idle_balance
kernel/sched/fair.c:9650 [inline]
#0: 0000000011891ec1 (&rq->lock){-.-.}, at:
pick_next_task_fair+0xb1f/0x15c0 kernel/sched/fair.c:6832
#1: 00000000627a8628 (rcu_read_lock){....}, at:
__update_idle_core+0x45/0x3f0 kernel/sched/fair.c:6049
1 lock held by khungtaskd/1035:
#0: 00000000627a8628 (rcu_read_lock){....}, at:
debug_show_all_locks+0x5f/0x27e kernel/locking/lockdep.c:4435
1 lock held by rsyslogd/7369:
#0: 000000003637083d (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110
fs/file.c:767
2 locks held by getty/7491:
#0: 0000000005113988 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 000000009bf2728f (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7492:
#0: 000000002e4d859a (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 00000000e23b9bbe (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7493:
#0: 00000000c4d4ecad (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 00000000ae2c46ca (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7494:
#0: 00000000b302f339 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 00000000a0413d51 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7495:
#0: 000000002ac73f99 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 0000000056393740 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7496:
#0: 000000000ec41afc (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 0000000054911d82 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7497:
#0: 000000009484c9a5 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 000000008fe37e92 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by kworker/1:1/23678:
#0: 0000000082033c25 ((wq_completion)"events"){+.+.}, at:
__write_once_size include/linux/compiler.h:220 [inline]
#0: 0000000082033c25 ((wq_completion)"events"){+.+.}, at:
arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: 0000000082033c25 ((wq_completion)"events"){+.+.}, at: atomic64_set
include/asm-generic/atomic-instrumented.h:40 [inline]
#0: 0000000082033c25 ((wq_completion)"events"){+.+.}, at: atomic_long_set
include/asm-generic/atomic-long.h:59 [inline]
#0: 0000000082033c25 ((wq_completion)"events"){+.+.}, at: set_work_data
kernel/workqueue.c:617 [inline]
#0: 0000000082033c25 ((wq_completion)"events"){+.+.}, at:
set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
#0: 0000000082033c25 ((wq_completion)"events"){+.+.}, at:
process_one_work+0x87e/0x1750 kernel/workqueue.c:2124
#1: 0000000046e20cf6 ((work_completion)(&m->wq)){+.+.}, at:
process_one_work+0x8b4/0x1750 kernel/workqueue.c:2128

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

NMI backtrace for cpu 0

CPU: 0 PID: 1035 Comm: khungtaskd Not tainted 4.19.67 #41

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:

__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
nmi_cpu_backtrace.cold+0x63/0xa4 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1b0/0x1f8 lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline]
watchdog+0x9df/0xee0 kernel/hung_task.c:287
kthread+0x354/0x420 kernel/kthread.c:246
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1

CPU: 1 PID: 23 Comm: kworker/u4:1 Not tainted 4.19.67 #41

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011

Workqueue: bat_events batadv_nc_worker
RIP: 0010:mark_lock+0x2f/0x1370 kernel/locking/lockdep.c:3095
Code: 89 d1 48 b8 00 00 00 00 00 fc ff df 48 89 e5 41 57 49 89 ff 41 56 41
89 d6 4c 89 ca 41 55 48 c1 ea 03 41 bd 01 00 00 00 41 54 <41> d3 e5 49 89
f4 53 48 83 ec 20 0f b6 04 02 84 c0 74 08 3c 01 0f
RSP: 0018:ffff8880aa39fb48 EFLAGS: 00000806
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: 0000000000000002
RDX: 1ffff11015471dd4 RSI: ffff8880aa38ee80 RDI: ffff8880aa38e600
RBP: ffff8880aa39fb68 R08: ffff8880aa38e600 R09: ffff8880aa38eea0
R10: 0000000000000000 R11: 0000000000000000 R12: ffff8880aa38ee80
R13: 0000000000000001 R14: 0000000000000002 R15: ffff8880aa38e600
FS: 0000000000000000(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fba1b38f140 CR3: 00000000a5e37000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
mark_held_locks+0xb1/0x100 kernel/locking/lockdep.c:2805
__trace_hardirqs_on_caller kernel/locking/lockdep.c:2826 [inline]
lockdep_hardirqs_on+0x19b/0x5d0 kernel/locking/lockdep.c:2879
trace_hardirqs_on+0x67/0x220 kernel/trace/trace_preemptirq.c:30
__local_bh_enable_ip+0x15a/0x270 kernel/softirq.c:194
__raw_spin_unlock_bh include/linux/spinlock_api_smp.h:176 [inline]
_raw_spin_unlock_bh+0x31/0x40 kernel/locking/spinlock.c:200
spin_unlock_bh include/linux/spinlock.h:374 [inline]
batadv_nc_purge_paths+0x265/0x370 net/batman-adv/network-coding.c:482
batadv_nc_worker+0x29c/0x760 net/batman-adv/network-coding.c:731
process_one_work+0x989/0x1750 kernel/workqueue.c:2153
worker_thread+0x98/0xe40 kernel/workqueue.c:2296
kthread+0x354/0x420 kernel/kthread.c:246
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: 97ab07e1 Linux 4.19.69
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=13945c56600000
kernel config: https://syzkaller.appspot.com/x/.config?x=a73820df154c3af

dashboard link: https://syzkaller.appspot.com/bug?extid=cb1a7299534706f76d88
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=163a0466600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+cb1a72...@syzkaller.appspotmail.com

audit: type=1400 audit(1567084621.354:39): avc: denied { map } for
pid=9749 comm="sh" path="/bin/dash" dev="sda1" ino=1473
scontext=system_u:system_r:insmod_t:s0-s0:c0.c1023
tcontext=system_u:object_r:file_t:s0 tclass=file permissive=1
INFO: task syz-executor.0:9746 blocked for more than 140 seconds.
Not tainted 4.19.69 #43

"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

syz-executor.0 D27912 9746 7499 0x00000004

RIP: 0033:0x459879
Code: 48 83 ec 28 48 89 6c 24 20 48 8d 6c 24 20 31 c0 48 8b 4c 24 38 eb 2d
48 89 44 24 18 48 8d 14 40 48 8b 5c 24 30 48 8d 14 d3 48 <89> 14 24 48 89
4c 24 08 e8 aa de ff ff 48 8b 4c 24 10 48 8b 44 24
RSP: 002b:00007f016a4d7c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000459879
RDX: 0000000020000140 RSI: 0000000020000000 RDI: 0000000000000000
RBP: 000000000075c118 R08: 0000000020000480 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f016a4d86d4
R13: 00000000004c5e2f R14: 00000000004da930 R15: 00000000ffffffff

Showing all locks held in the system:

1 lock held by khungtaskd/1037:
#0: 00000000ebe80c88 (rcu_read_lock){....}, at:
debug_show_all_locks+0x5f/0x27e kernel/locking/lockdep.c:4435
1 lock held by rsyslogd/7331:
#0: 000000001c963945 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110
fs/file.c:767
2 locks held by getty/7453:
#0: 0000000077e96566 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 000000009ffb5abc (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7454:
#0: 00000000ea3b6ae0 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 00000000ab2f9a12 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7455:
#0: 0000000076f655cb (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 00000000545def72 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7456:
#0: 000000004d5637fe (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 000000001609fae9 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7457:
#0: 00000000b1d2b2ba (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 00000000c7e06395 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7458:
#0: 0000000091cad16c (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 00000000fef30326 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7459:
#0: 000000004e2bd4c6 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:362
#1: 000000005925f7f4 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by kworker/0:0/7501:
#0: 00000000f8910056 ((wq_completion)"events"){+.+.}, at:
__write_once_size include/linux/compiler.h:220 [inline]
#0: 00000000f8910056 ((wq_completion)"events"){+.+.}, at:
arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: 00000000f8910056 ((wq_completion)"events"){+.+.}, at: atomic64_set
include/asm-generic/atomic-instrumented.h:40 [inline]
#0: 00000000f8910056 ((wq_completion)"events"){+.+.}, at: atomic_long_set
include/asm-generic/atomic-long.h:59 [inline]
#0: 00000000f8910056 ((wq_completion)"events"){+.+.}, at: set_work_data
kernel/workqueue.c:617 [inline]
#0: 00000000f8910056 ((wq_completion)"events"){+.+.}, at:
set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
#0: 00000000f8910056 ((wq_completion)"events"){+.+.}, at:
process_one_work+0x87e/0x1750 kernel/workqueue.c:2124
#1: 0000000005d31f3b ((work_completion)(&m->wq)){+.+.}, at:

process_one_work+0x8b4/0x1750 kernel/workqueue.c:2128

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

NMI backtrace for cpu 0

CPU: 0 PID: 1037 Comm: khungtaskd Not tainted 4.19.69 #43

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x172/0x1f0 lib/dump_stack.c:113
nmi_cpu_backtrace.cold+0x63/0xa4 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1b0/0x1f8 lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline]
watchdog+0x9df/0xee0 kernel/hung_task.c:287
kthread+0x354/0x420 kernel/kthread.c:246
ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
Sending NMI from CPU 0 to CPUs 1:

NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0xe/0x10
arch/x86/include/asm/irqflags.h:60

[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: 2cae3e25 Linux 4.19.179
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11ca99bcd00000
kernel config: https://syzkaller.appspot.com/x/.config?x=6362bb600ad8bf7
dashboard link: https://syzkaller.appspot.com/bug?extid=cb1a7299534706f76d88
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=122d9cfad00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=171bd656d00000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cb1a72...@syzkaller.appspotmail.com

INFO: task syz-executor239:8097 blocked for more than 140 seconds.
Not tainted 4.19.179-syzkaller #0

"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.

syz-executor239 D28072 8097 8086 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2828 [inline]
__schedule+0x887/0x2040 kernel/sched/core.c:3517
schedule+0x8d/0x1b0 kernel/sched/core.c:3561
schedule_timeout+0x92d/0xfe0 kernel/time/timer.c:1794

do_wait_for_common kernel/sched/completion.c:83 [inline]
__wait_for_common kernel/sched/completion.c:104 [inline]

wait_for_common+0x29c/0x470 kernel/sched/completion.c:115
__flush_work+0x4bb/0x8b0 kernel/workqueue.c:2925
__cancel_work_timer+0x412/0x590 kernel/workqueue.c:3012
p9_conn_destroy net/9p/trans_fd.c:899 [inline]
p9_fd_close+0x29c/0x520 net/9p/trans_fd.c:934
p9_client_create+0x901/0x12e0 net/9p/client.c:1084
v9fs_session_init+0x1dd/0x1770 fs/9p/v9fs.c:421
v9fs_mount+0x73/0x910 fs/9p/vfs_super.c:135
mount_fs+0xa3/0x310 fs/super.c:1261
vfs_kern_mount.part.0+0x68/0x470 fs/namespace.c:961

vfs_kern_mount fs/namespace.c:951 [inline]
do_new_mount fs/namespace.c:2469 [inline]

do_mount+0x113c/0x2f10 fs/namespace.c:2799
ksys_mount+0xcf/0x130 fs/namespace.c:3015

__do_sys_mount fs/namespace.c:3029 [inline]
__se_sys_mount fs/namespace.c:3026 [inline]

__x64_sys_mount+0xba/0x150 fs/namespace.c:3026
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445c39
Code: Bad RIP value.
RSP: 002b:00007f949bc47308 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00000000004cb518 RCX: 0000000000445c39
RDX: 0000000020000040 RSI: 0000000020000000 RDI: 0000000000000000
RBP: 00000000004cb510 R08: 00000000200001c0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000004cb51c
R13: 000000000049b07c R14: 64663d736e617274 R15: 0000000000022000

Showing all locks held in the system:

2 locks held by kworker/0:1/14:
#0: 0000000094edc173 ((wq_completion)"events"){+.+.}, at: process_one_work+0x767/0x1570 kernel/workqueue.c:2123
#1: 00000000335ecea8 ((work_completion)(&m->rq)){+.+.}, at: process_one_work+0x79c/0x1570 kernel/workqueue.c:2127
1 lock held by khungtaskd/1567:
#0: 00000000aa0a327e (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x265 kernel/locking/lockdep.c:4440

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

NMI backtrace for cpu 0

CPU: 0 PID: 1567 Comm: khungtaskd Not tainted 4.19.179-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]

dump_stack+0x1fc/0x2ef lib/dump_stack.c:118
nmi_cpu_backtrace.cold+0x63/0xa2 lib/nmi_backtrace.c:101
nmi_trigger_cpumask_backtrace+0x1a6/0x1f0 lib/nmi_backtrace.c:62

trigger_all_cpu_backtrace include/linux/nmi.h:146 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:203 [inline]

watchdog+0x991/0xe60 kernel/hung_task.c:287
kthread+0x33f/0x460 kernel/kthread.c:259

ret_from_fork+0x24/0x30 arch/x86/entry/entry_64.S:415
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1

CPU: 1 PID: 4691 Comm: systemd-journal Not tainted 4.19.179-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

RIP: 0010:orc_find arch/x86/kernel/unwind_orc.c:149 [inline]
RIP: 0010:unwind_next_frame+0x231/0x1c60 arch/x86/kernel/unwind_orc.c:422
Code: ff 39 d6 0f 83 df 10 00 00 48 ba 00 00 00 00 00 fc ff df 41 89 f0 4a 8d 3c 85 f8 27 17 8c 49 89 f9 49 c1 e9 03 45 0f b6 0c 11 <48> 89 fa 83 e2 07 83 c2 03 44 38 ca 7c 32 45 84 c9 74 2d 4c 89 44
RSP: 0018:ffff8880a0effa08 EFLAGS: 00000a07
RAX: 0000000000000000 RBX: 1ffff110141dff49 RCX: ffffffff8197d35f
RDX: dffffc0000000000 RSI: 00000000000097d3 RDI: ffffffff8c198744
RBP: 0000000000000001 R08: 00000000000097d3 R09: 0000000000000000
R10: 0000000000074071 R11: 0000000000000001 R12: ffff8880a0effb38
R13: ffff8880a0effb25 R14: ffff8880a0effb28 R15: ffff8880a0effaf0
FS: 00007f7ba8b8d8c0(0000) GS:ffff8880ba100000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 00007f7ba5f61578 CR3: 00000000a0ce8000 CR4: 00000000001406e0

DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:

__save_stack_trace+0x9f/0x190 arch/x86/kernel/stacktrace.c:44
save_stack mm/kasan/kasan.c:448 [inline]
set_track mm/kasan/kasan.c:460 [inline]
kasan_kmalloc+0xeb/0x160 mm/kasan/kasan.c:553
slab_post_alloc_hook mm/slab.h:445 [inline]
slab_alloc mm/slab.c:3397 [inline]
kmem_cache_alloc+0x110/0x370 mm/slab.c:3557
getname_flags+0xce/0x590 fs/namei.c:140
do_sys_open+0x26c/0x520 fs/open.c:1079
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7f7ba811d840
Code: 73 01 c3 48 8b 0d 68 77 20 00 f7 d8 64 89 01 48 83 c8 ff c3 66 0f 1f 44 00 00 83 3d 89 bb 20 00 00 75 10 b8 02 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 1e f6 ff ff 48 89 04 24
RSP: 002b:00007ffd2aa1a738 EFLAGS: 00000246 ORIG_RAX: 0000000000000002
RAX: ffffffffffffffda RBX: 00007ffd2aa1aa40 RCX: 00007f7ba811d840
RDX: 00000000000001a0 RSI: 0000000000080042 RDI: 00005564bef656d0
RBP: 000000000000000d R08: 000000000000ffc0 R09: 00000000ffffffff
R10: 0000000000000069 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00005564bef58040 R14: 00007ffd2aa1aa00 R15: 00005564bef65720