INFO: task hung in iterate_supers

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 7250956f Linux 4.19.61
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=106967f4600000
kernel config: https://syzkaller.appspot.com/x/.config?x=13e37a4c57ecad7f
dashboard link: https://syzkaller.appspot.com/bug?extid=f6f3a910fd426719ea8d
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+f6f3a9...@syzkaller.appspotmail.com

overlayfs: unrecognized mount option "upp=Vx� @cqFile0" or missing value
INFO: task syz-executor.1:8344 blocked for more than 140 seconds.
Not tainted 4.19.61 #35
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.1 D28480 8344 7696 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
__rwsem_down_read_failed_common kernel/locking/rwsem-xadd.c:292 [inline]
rwsem_down_read_failed+0x21b/0x3c0 kernel/locking/rwsem-xadd.c:309
call_rwsem_down_read_failed+0x18/0x30 arch/x86/lib/rwsem.S:94
__down_read arch/x86/include/asm/rwsem.h:83 [inline]
down_read+0x49/0xb0 kernel/locking/rwsem.c:26
iterate_supers+0xe2/0x290 fs/super.c:631
ksys_sync+0x90/0x160 fs/sync.c:113
__ia32_sys_sync+0xe/0x20 fs/sync.c:124
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 5c d2 37 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:00007ffb94f87c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a2
RAX: ffffffffffffffda RBX: 000000000075bf28 RCX: 0000000000459829
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 000000000075bf20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffb94f886d4
R13: 00000000004c6471 R14: 00000000004df398 R15: 00000000ffffffff

Showing all locks held in the system:
1 lock held by khungtaskd/1037:
#0: 000000005dce8550 (rcu_read_lock){....}, at:
debug_show_all_locks+0x5f/0x27e kernel/locking/lockdep.c:4435
1 lock held by rsyslogd/7530:
#0: 00000000090b9823 (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110
fs/file.c:767
2 locks held by getty/7651:
#0: 000000007affbc4b (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 00000000137ac9fc (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7652:
#0: 00000000b72a5c2a (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 00000000ff36d076 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7653:
#0: 000000004d058a65 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 000000007634a822 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7654:
#0: 000000002bed3e62 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 00000000d04e4d5b (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7655:
#0: 00000000a6702333 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 000000004fe6c46c (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7656:
#0: 00000000537bc4f0 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 00000000cdd1f1f8 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7657:
#0: 00000000f11b423e (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 0000000011a3c309 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
1 lock held by syz-executor.0/8327:
#0: 00000000a302748b (&type->s_umount_key#61/1){+.+.}, at: alloc_super
fs/super.c:226 [inline]
#0: 00000000a302748b (&type->s_umount_key#61/1){+.+.}, at:
sget_userns+0x208/0xd30 fs/super.c:519
1 lock held by syz-executor.1/8344:
#0: 00000000a302748b (&type->s_umount_key#62){.+.+}, at:
iterate_supers+0xe2/0x290 fs/super.c:631

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

NMI backtrace for cpu 0
CPU: 0 PID: 1037 Comm: khungtaskd Not tainted 4.19.61 #35
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


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.