INFO: task hung in lock_mount (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 4938296e03bd Linux 4.19.198
git tree: linux-4.19.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11d7e2b2300000
kernel config: https://syzkaller.appspot.com/x/.config?x=9013c716691ad1fe
dashboard link: https://syzkaller.appspot.com/bug?extid=183b1203a047848d6123
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

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

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+183b12...@syzkaller.appspotmail.com

Bluetooth: hci3: command 0x0406 tx timeout
ieee802154 phy0 wpan0: encryption failed: -22
ieee802154 phy1 wpan1: encryption failed: -22
ieee802154 phy0 wpan0: encryption failed: -22
ieee802154 phy1 wpan1: encryption failed: -22
INFO: task syz-executor.2:17120 blocked for more than 140 seconds.
Not tainted 4.19.198-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
syz-executor.2 D28224 17120 8111 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
__rwsem_down_write_failed_common kernel/locking/rwsem-xadd.c:589 [inline]
rwsem_down_write_failed+0x3aa/0x760 kernel/locking/rwsem-xadd.c:618
call_rwsem_down_write_failed+0x13/0x20 arch/x86/lib/rwsem.S:117
__down_write arch/x86/include/asm/rwsem.h:142 [inline]
down_write+0x4f/0x90 kernel/locking/rwsem.c:72
inode_lock include/linux/fs.h:748 [inline]
lock_mount+0xcc/0x4a0 fs/namespace.c:2039
do_add_mount+0x73/0x560 fs/namespace.c:2416
do_new_mount fs/namespace.c:2483 [inline]
do_mount+0x1956/0x2f10 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: 0033:0x4665e9
Code: Bad RIP value.
RSP: 002b:00007f47ef4aa188 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 000000000056c0f0 RCX: 00000000004665e9
RDX: 0000000020000280 RSI: 00000000200002c0 RDI: 0000000000000000
RBP: 00000000004bfcc4 R08: 0000000020000140 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056c0f0
R13: 00007ffcae5aa52f R14: 00007f47ef4aa300 R15: 0000000000022000

Showing all locks held in the system:
1 lock held by khungtaskd/1571:
#0: 00000000bb7f7a1b (rcu_read_lock){....}, at: debug_show_all_locks+0x53/0x265 kernel/locking/lockdep.c:4441
2 locks held by syz-executor.2/17073:
#0: 00000000bbbda3f8 (sb_writers#15){.+.+}, at: sb_start_write include/linux/fs.h:1579 [inline]
#0: 00000000bbbda3f8 (sb_writers#15){.+.+}, at: mnt_want_write+0x3a/0xb0 fs/namespace.c:360
#1: 00000000de73859f (&sb->s_type->i_mutex_key#23/1){+.+.}, at: inode_lock_nested include/linux/fs.h:783 [inline]
#1: 00000000de73859f (&sb->s_type->i_mutex_key#23/1){+.+.}, at: filename_create+0x15a/0x490 fs/namei.c:3638
1 lock held by syz-executor.2/17120:
#0: 00000000de73859f (&sb->s_type->i_mutex_key#23){+.+.}, at: inode_lock include/linux/fs.h:748 [inline]
#0: 00000000de73859f (&sb->s_type->i_mutex_key#23){+.+.}, at: lock_mount+0xcc/0x4a0 fs/namespace.c:2039

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

NMI backtrace for cpu 0
CPU: 0 PID: 1571 Comm: khungtaskd Not tainted 4.19.198-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: 7758 Comm: rs:main Q:Reg Not tainted 4.19.198-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:ext4_da_should_update_i_disksize fs/ext4/inode.c:3149 [inline]
RIP: 0010:ext4_da_write_end+0x2fa/0xa70 fs/ext4/inode.c:3185
Code: 85 24 07 00 00 0f b6 88 c2 00 00 00 4c 89 ea 31 ff 81 e2 ff 0f 00 00 48 8d 5c 1a ff 48 d3 eb 89 de 89 5c 24 30 e8 c6 9b 81 ff <85> db 74 58 89 d8 48 89 6c 24 38 31 db 8b 6c 24 30 44 89 64 24 30
RSP: 0018:ffff888094e07a00 EFLAGS: 00000293
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff81e0e7ca
RDX: 0000000000000000 RSI: ffff888093e1c380 RDI: 0000000000000005
RBP: ffff888099ff5730 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000005 R11: 0000000000000000 R12: 00000000000001a2
R13: 0000000000066000 R14: 00000000000001a2 R15: ffff88803e557930
FS: 00007fd7eac63700(0000) GS:ffff8880ba100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fb796530000 CR3: 00000000b35fb000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
generic_perform_write+0x2ae/0x4d0 mm/filemap.c:3181
__generic_file_write_iter+0x24b/0x610 mm/filemap.c:3295
ext4_file_write_iter+0x2fe/0xf20 fs/ext4/file.c:272
call_write_iter include/linux/fs.h:1821 [inline]
new_sync_write fs/read_write.c:474 [inline]
__vfs_write+0x51b/0x770 fs/read_write.c:487
vfs_write+0x1f3/0x540 fs/read_write.c:549
ksys_write+0x12b/0x2a0 fs/read_write.c:599
do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x7fd7ed6a71cd
Code: c2 20 00 00 75 10 b8 01 00 00 00 0f 05 48 3d 01 f0 ff ff 73 31 c3 48 83 ec 08 e8 ae fc ff ff 48 89 04 24 b8 01 00 00 00 0f 05 <48> 8b 3c 24 48 89 c2 e8 f7 fc ff ff 48 89 d0 48 83 c4 08 48 3d 01
RSP: 002b:00007fd7eac62590 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fd7e0022760 RCX: 00007fd7ed6a71cd
RDX: 0000000000000403 RSI: 00007fd7e0022760 RDI: 0000000000000006
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000293 R12: 00007fd7e00224e0
R13: 00007fd7eac625b0 R14: 000055fa7edf4360 R15: 0000000000000403


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[syzbot]

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