INFO: task hung in __fuse_request_send

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 6500aa43 Linux 4.19.52
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17e210c6a00000
kernel config: https://syzkaller.appspot.com/x/.config?x=c23804fab7069177
dashboard link: https://syzkaller.appspot.com/bug?extid=9a6bd350433f4ec03f80
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16416121a00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=10262632a00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+9a6bd3...@syzkaller.appspotmail.com

audit: type=1400 audit(1560834043.453:36): avc: denied { map } for
pid=7858 comm="syz-executor014" path="/root/syz-executor014331539"
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-executor014:7859 blocked for more than 140 seconds.
Not tainted 4.19.52 #24
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor014 D26976 7859 7856 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x80d/0x1c70 kernel/sched/core.c:3474
schedule+0x92/0x1c0 kernel/sched/core.c:3518
request_wait_answer+0x42f/0x7c0 fs/fuse/dev.c:485
__fuse_request_send+0x128/0x1d0 fs/fuse/dev.c:505
fuse_request_send+0x60/0xa0 fs/fuse/dev.c:518
fuse_simple_request+0x2f6/0x720 fs/fuse/dev.c:576
fuse_lookup_name+0x275/0x670 fs/fuse/dir.c:323
fuse_lookup+0xeb/0x3e0 fs/fuse/dir.c:361
__lookup_slow+0x279/0x500 fs/namei.c:1671
lookup_slow+0x58/0x80 fs/namei.c:1688
walk_component+0x747/0x2000 fs/namei.c:1810
lookup_last fs/namei.c:2273 [inline]
path_lookupat.isra.0+0x1f5/0x8d0 fs/namei.c:2318
filename_lookup+0x1b0/0x410 fs/namei.c:2348
user_path_at_empty+0x43/0x50 fs/namei.c:2608
user_path_at include/linux/namei.h:57 [inline]
vfs_statx+0x129/0x200 fs/stat.c:185
vfs_stat include/linux/fs.h:3126 [inline]
__do_sys_newstat+0xa4/0x130 fs/stat.c:337
__se_sys_newstat fs/stat.c:333 [inline]
__x64_sys_newstat+0x54/0x80 fs/stat.c:333
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445b79
Code: Bad RIP value.
RSP: 002b:00007f735b782db8 EFLAGS: 00000246 ORIG_RAX: 0000000000000004
RAX: ffffffffffffffda RBX: 00000000006dac28 RCX: 0000000000445b79
RDX: 0000000000000031 RSI: 0000000000000000 RDI: 0000000020000580
RBP: 00000000006dac20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dac2c
R13: 00007ffee7f1630f R14: 00007f735b7839c0 R15: 20c49ba5e353f7cf
INFO: task syz-executor014:7861 blocked for more than 140 seconds.
Not tainted 4.19.52 #24
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor014 D28632 7861 7856 0x00000004
Call Trace:
context_switch kernel/sched/core.c:2826 [inline]
__schedule+0x80d/0x1c70 kernel/sched/core.c:3474
schedule+0x92/0x1c0 kernel/sched/core.c:3518
__rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:589 [inline]
rwsem_down_write_failed+0x774/0xc30 kernel/locking/rwsem-xadd.c:618
call_rwsem_down_write_failed+0x17/0x30 arch/x86/lib/rwsem.S:117
__down_write arch/x86/include/asm/rwsem.h:142 [inline]
down_write+0x53/0x90 kernel/locking/rwsem.c:72
inode_lock include/linux/fs.h:747 [inline]
fuse_reverse_inval_entry+0xaf/0x6d0 fs/fuse/dir.c:977
fuse_notify_delete fs/fuse/dev.c:1565 [inline]
fuse_notify fs/fuse/dev.c:1799 [inline]
fuse_dev_do_write+0xd44/0x25a0 fs/fuse/dev.c:1874
fuse_dev_write+0x158/0x1f0 fs/fuse/dev.c:1958
call_write_iter include/linux/fs.h:1820 [inline]
new_sync_write fs/read_write.c:474 [inline]
__vfs_write+0x587/0x810 fs/read_write.c:487
vfs_write+0x20c/0x560 fs/read_write.c:549
ksys_write+0x14f/0x2d0 fs/read_write.c:599
__do_sys_write fs/read_write.c:611 [inline]
__se_sys_write fs/read_write.c:608 [inline]
__x64_sys_write+0x73/0xb0 fs/read_write.c:608
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x445b79
Code: Bad RIP value.
RSP: 002b:00007f735b740db8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00000000006dac48 RCX: 0000000000445b79
RDX: 000000000000002e RSI: 0000000020000000 RDI: 0000000000000003
RBP: 00000000006dac40 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dac4c
R13: 00007ffee7f1630f R14: 00007f735b7419c0 R15: 20c49ba5e353f7cf

Showing all locks held in the system:
1 lock held by khungtaskd/1033:
#0: 0000000079a1f957 (rcu_read_lock){....}, at:
debug_show_all_locks+0x5f/0x27e kernel/locking/lockdep.c:4435
2 locks held by rsyslogd/7710:
#0: 00000000f1eb65be (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110
fs/file.c:767
#1: 00000000de96d753 (&rq->lock){-.-.}, at: syslog_print
kernel/printk/printk.c:1310 [inline]
#1: 00000000de96d753 (&rq->lock){-.-.}, at: do_syslog
kernel/printk/printk.c:1470 [inline]
#1: 00000000de96d753 (&rq->lock){-.-.}, at: do_syslog+0xa6d/0x1690
kernel/printk/printk.c:1444
2 locks held by getty/7832:
#0: 0000000039fec607 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 000000009ac432e4 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7833:
#0: 0000000093e089fe (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 0000000045b9fd21 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7834:
#0: 000000005f9d69ea (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 00000000e39969ed (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7835:
#0: 00000000b7dfcbc7 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 00000000859d12db (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7836:
#0: 00000000048e4e52 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 00000000d9553838 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7837:
#0: 00000000a2d2918d (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 0000000072c8acd7 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7838:
#0: 00000000f4396991 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 00000000c537132f (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by syz-executor014/7859:
#0: 0000000058d0b455 (&type->i_mutex_dir_key#6){++++}, at:
inode_lock_shared include/linux/fs.h:757 [inline]
#0: 0000000058d0b455 (&type->i_mutex_dir_key#6){++++}, at:
lookup_slow+0x4a/0x80 fs/namei.c:1687
#1: 000000002d9bb59e (&fi->mutex){+.+.}, at: fuse_lock_inode+0xba/0xf0
fs/fuse/inode.c:365
2 locks held by syz-executor014/7861:
#0: 00000000210ec71c (&fc->killsb){.+.+}, at: fuse_notify_delete
fs/fuse/dev.c:1562 [inline]
#0: 00000000210ec71c (&fc->killsb){.+.+}, at: fuse_notify
fs/fuse/dev.c:1799 [inline]
#0: 00000000210ec71c (&fc->killsb){.+.+}, at:
fuse_dev_do_write+0x1f86/0x25a0 fs/fuse/dev.c:1874
#1: 0000000058d0b455 (&type->i_mutex_dir_key#6){++++}, at: inode_lock
include/linux/fs.h:747 [inline]
#1: 0000000058d0b455 (&type->i_mutex_dir_key#6){++++}, at:
fuse_reverse_inval_entry+0xaf/0x6d0 fs/fuse/dir.c:977

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

NMI backtrace for cpu 1
CPU: 1 PID: 1033 Comm: khungtaskd Not tainted 4.19.52 #24
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 1 to CPUs 0:
NMI backtrace for cpu 0 skipped: idling at native_safe_halt+0xe/0x10
arch/x86/include/asm/irqflags.h:60


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