INFO: task hung in filename_create

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 893af1c7 Linux 4.19.66
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=15cc7716600000
kernel config: https://syzkaller.appspot.com/x/.config?x=d5fac5a8617b8643
dashboard link: https://syzkaller.appspot.com/bug?extid=d0cbe5efb6e8567f8206
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+d0cbe5...@syzkaller.appspotmail.com

audit: type=1400 audit(1565537330.268:57): avc: denied { map_read
map_write } for pid=8360 comm="syz-executor.4"
scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=bpf
permissive=1
INFO: task syz-executor.5:8342 blocked for more than 140 seconds.
Not tainted 4.19.66 #40
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5 D29288 8342 7803 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_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_nested+0x57/0x90 kernel/locking/rwsem.c:194
inode_lock_nested include/linux/fs.h:782 [inline]
filename_create+0x17c/0x4f0 fs/namei.c:3635
user_path_create fs/namei.c:3693 [inline]
do_mkdirat+0xb5/0x2a0 fs/namei.c:3831
__do_sys_mkdir fs/namei.c:3855 [inline]
__se_sys_mkdir fs/namei.c:3853 [inline]
__x64_sys_mkdir+0x5c/0x80 fs/namei.c:3853
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459829
Code: Bad RIP value.
RSP: 002b:00007f743de5ac78 EFLAGS: 00000246 ORIG_RAX: 0000000000000053
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 0000000000459829
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000080
RBP: 000000000075bfc8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f743de5b6d4
R13: 00000000004bf021 R14: 00000000004da660 R15: 00000000ffffffff
INFO: task syz-executor.5:8343 blocked for more than 140 seconds.
Not tainted 4.19.66 #40
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5 D28176 8343 7803 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
inode_lock_shared include/linux/fs.h:757 [inline]
lookup_slow+0x4a/0x80 fs/namei.c:1687
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_lstat include/linux/fs.h:3133 [inline]
__do_sys_newlstat+0xa4/0x130 fs/stat.c:350
__se_sys_newlstat fs/stat.c:344 [inline]
__x64_sys_newlstat+0x54/0x80 fs/stat.c:344
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459829
Code: Bad RIP value.
RSP: 002b:00007f743de39c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000006
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 0000000000459829
RDX: 0000000000000000 RSI: 0000000020000480 RDI: 0000000020000180
RBP: 000000000075c070 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f743de3a6d4
R13: 00000000004c5c7f R14: 00000000004da5b8 R15: 00000000ffffffff
INFO: task syz-executor.5:8344 blocked for more than 140 seconds.
Not tainted 4.19.66 #40
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5 D29304 8344 7803 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
inode_lock_shared include/linux/fs.h:757 [inline]
lookup_slow+0x4a/0x80 fs/namei.c:1687
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]
ksys_chdir+0x98/0x1f0 fs/open.c:458
__do_sys_chdir fs/open.c:480 [inline]
__se_sys_chdir fs/open.c:478 [inline]
__x64_sys_chdir+0x31/0x40 fs/open.c:478
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459829
Code: Bad RIP value.
RSP: 002b:00007f743de18c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000050
RAX: ffffffffffffffda RBX: 0000000000000001 RCX: 0000000000459829
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000000
RBP: 000000000075c118 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f743de196d4
R13: 00000000004bf08a R14: 00000000004d1960 R15: 00000000ffffffff
INFO: task syz-executor.5:8345 blocked for more than 140 seconds.
Not tainted 4.19.66 #40
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5 D29048 8345 7803 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
inode_lock_shared include/linux/fs.h:757 [inline]
lookup_slow+0x4a/0x80 fs/namei.c:1687
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 include/linux/namei.h:62 [inline]
do_mount+0x150/0x2bc0 fs/namespace.c:2739
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: Bad RIP value.
RSP: 002b:00007f743ddf7c78 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0000000000000005 RCX: 0000000000459829
RDX: 0000000020000300 RSI: 0000000020000200 RDI: 0000000000000000
RBP: 000000000075c1c0 R08: 00000000200005c0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f743ddf86d4
R13: 00000000004c5dcf R14: 00000000004da870 R15: 00000000ffffffff
INFO: task syz-executor.5:8346 blocked for more than 140 seconds.
Not tainted 4.19.66 #40
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.5 D29560 8346 7803 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
inode_lock_shared include/linux/fs.h:757 [inline]
lookup_slow+0x4a/0x80 fs/namei.c:1687
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]
do_sys_truncate.part.0+0x92/0x150 fs/open.c:130
do_sys_truncate fs/open.c:126 [inline]
__do_sys_truncate fs/open.c:144 [inline]
__se_sys_truncate fs/open.c:142 [inline]
__x64_sys_truncate+0x6e/0xa0 fs/open.c:142
do_syscall_64+0xfd/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x459829
Code: Bad RIP value.
RSP: 002b:00007f743ddd6c78 EFLAGS: 00000246 ORIG_RAX: 000000000000004c
RAX: ffffffffffffffda RBX: 0000000000000002 RCX: 0000000000459829
RDX: 0000000000000000 RSI: 0000000000000006 RDI: 0000000020000040
RBP: 000000000075c268 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f743ddd76d4
R13: 00000000004c0263 R14: 00000000004e00a8 R15: 00000000ffffffff

Showing all locks held in the system:
2 locks held by kworker/u4:5/520:
#0: 00000000bea1c2ad (&rq->lock){-.-.}, at: rq_lock
kernel/sched/sched.h:1821 [inline]
#0: 00000000bea1c2ad (&rq->lock){-.-.}, at: __schedule+0x1f8/0x1dc0
kernel/sched/core.c:3412
#1: 000000003109e8cd (rcu_read_lock){....}, at:
__update_idle_core+0x45/0x3f0 kernel/sched/fair.c:6049
1 lock held by khungtaskd/1038:
#0: 000000003109e8cd (rcu_read_lock){....}, at:
debug_show_all_locks+0x5f/0x27e kernel/locking/lockdep.c:4435
1 lock held by rsyslogd/7621:
#0: 000000006d8dcebf (&f->f_pos_lock){+.+.}, at: __fdget_pos+0xee/0x110
fs/file.c:767
2 locks held by getty/7744:
#0: 00000000d7360469 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 0000000000ecf304 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7745:
#0: 00000000d5e83c5d (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 00000000c4d7bb11 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7746:
#0: 00000000ebc62736 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 0000000004f0e78c (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7747:
#0: 00000000f7e15783 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 00000000178dfb8a (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7748:
#0: 00000000f63e09a7 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 00000000b957740a (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7749:
#0: 0000000082ecb1cc (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 0000000092b53b56 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
2 locks held by getty/7750:
#0: 00000000d0c4a965 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x33/0x40 drivers/tty/tty_ldsem.c:363
#1: 000000003dec704c (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x232/0x1b30 drivers/tty/n_tty.c:2154
1 lock held by syz-executor.5/8330:
#0: 00000000ab6f67e4 (&sb->s_type->i_mutex_key#21){.+.+}, at:
inode_lock_shared include/linux/fs.h:757 [inline]
#0: 00000000ab6f67e4 (&sb->s_type->i_mutex_key#21){.+.+}, at:
lookup_slow+0x4a/0x80 fs/namei.c:1687
2 locks held by syz-executor.5/8342:
#0: 00000000231d55e8 (sb_writers#15){.+.+}, at: sb_start_write
include/linux/fs.h:1578 [inline]
#0: 00000000231d55e8 (sb_writers#15){.+.+}, at: mnt_want_write+0x3f/0xc0
fs/namespace.c:360
#1: 00000000ab6f67e4 (&sb->s_type->i_mutex_key#21/1){+.+.}, at:
inode_lock_nested include/linux/fs.h:782 [inline]
#1: 00000000ab6f67e4 (&sb->s_type->i_mutex_key#21/1){+.+.}, at:
filename_create+0x17c/0x4f0 fs/namei.c:3635
1 lock held by syz-executor.5/8343:
#0: 00000000ab6f67e4 (&sb->s_type->i_mutex_key#21){.+.+}, at:
inode_lock_shared include/linux/fs.h:757 [inline]
#0: 00000000ab6f67e4 (&sb->s_type->i_mutex_key#21){.+.+}, at:
lookup_slow+0x4a/0x80 fs/namei.c:1687
1 lock held by syz-executor.5/8344:
#0: 00000000ab6f67e4 (&sb->s_type->i_mutex_key#21){.+.+}, at:
inode_lock_shared include/linux/fs.h:757 [inline]
#0: 00000000ab6f67e4 (&sb->s_type->i_mutex_key#21){.+.+}, at:
lookup_slow+0x4a/0x80 fs/namei.c:1687
1 lock held by syz-executor.5/8345:
#0: 00000000ab6f67e4 (&sb->s_type->i_mutex_key#21){.+.+}, at:
inode_lock_shared include/linux/fs.h:757 [inline]
#0: 00000000ab6f67e4 (&sb->s_type->i_mutex_key#21){.+.+}, at:
lookup_slow+0x4a/0x80 fs/namei.c:1687
1 lock held by syz-executor.5/8346:
#0: 00000000ab6f67e4 (&sb->s_type->i_mutex_key#21){.+.+}, at:
inode_lock_shared include/linux/fs.h:757 [inline]
#0: 00000000ab6f67e4 (&sb->s_type->i_mutex_key#21){.+.+}, at:
lookup_slow+0x4a/0x80 fs/namei.c:1687

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

NMI backtrace for cpu 0
CPU: 0 PID: 1038 Comm: khungtaskd Not tainted 4.19.66 #40
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.