[v5.15] INFO: task hung in lock_mount

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: c52b9710c83d Linux 5.15.156
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=11740a9b180000
kernel config: https://syzkaller.appspot.com/x/.config?x=567b6ddc38438433
dashboard link: https://syzkaller.appspot.com/bug?extid=186cfa1ab5ab413e8877
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1420ec5f180000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1651610f180000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/1bd4b9969373/disk-c52b9710.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/10509e89bd25/vmlinux-c52b9710.xz
kernel image: https://storage.googleapis.com/syzbot-assets/a623a4c52eb5/bzImage-c52b9710.xz
mounted in repro: https://storage.googleapis.com/syzbot-assets/54e13578a03f/mount_2.gz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+186cfa...@syzkaller.appspotmail.com

INFO: task syz-executor245:3534 blocked for more than 143 seconds.
Not tainted 5.15.156-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor245 state:D stack:25824 pid: 3534 ppid: 3531 flags:0x00004006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5030 [inline]
__schedule+0x12c4/0x45b0 kernel/sched/core.c:6376
schedule+0x11b/0x1f0 kernel/sched/core.c:6459
rwsem_down_write_slowpath+0xf0c/0x16a0 kernel/locking/rwsem.c:1165
inode_lock include/linux/fs.h:789 [inline]
lock_mount+0x62/0x2c0 fs/namespace.c:2248
do_new_mount_fc fs/namespace.c:2942 [inline]
do_new_mount+0x433/0xb40 fs/namespace.c:3007
do_mount fs/namespace.c:3348 [inline]
__do_sys_mount fs/namespace.c:3556 [inline]
__se_sys_mount+0x2d5/0x3c0 fs/namespace.c:3533
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f34356fa26a
RSP: 002b:00007fff46c5c9d8 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fff46c5c9f0 RCX: 00007f34356fa26a
RDX: 0000000020001500 RSI: 0000000020000140 RDI: 00007fff46c5c9f0
RBP: 0000000000000005 R08: 00007fff46c5ca30 R09: 00000000000014f8
R10: 0000000000000800 R11: 0000000000000286 R12: 0000000000000800
R13: 00007fff46c5ca30 R14: 0000000000000004 R15: 0000000000020000
</TASK>
INFO: task syz-executor245:3535 blocked for more than 143 seconds.
Not tainted 5.15.156-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor245 state:D stack:24864 pid: 3535 ppid: 3530 flags:0x00004006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5030 [inline]
__schedule+0x12c4/0x45b0 kernel/sched/core.c:6376
schedule+0x11b/0x1f0 kernel/sched/core.c:6459
rwsem_down_write_slowpath+0xf0c/0x16a0 kernel/locking/rwsem.c:1165
inode_lock include/linux/fs.h:789 [inline]
lock_mount+0x21b/0x2c0 fs/namespace.c:2248
do_new_mount_fc fs/namespace.c:2942 [inline]
do_new_mount+0x433/0xb40 fs/namespace.c:3007
do_mount fs/namespace.c:3348 [inline]
__do_sys_mount fs/namespace.c:3556 [inline]
__se_sys_mount+0x2d5/0x3c0 fs/namespace.c:3533
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f34356fa26a
RSP: 002b:00007fff46c5c9d8 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fff46c5c9f0 RCX: 00007f34356fa26a
RDX: 0000000020001500 RSI: 0000000020000140 RDI: 00007fff46c5c9f0
RBP: 0000000000000005 R08: 00007fff46c5ca30 R09: 00000000000014f8
R10: 0000000000000800 R11: 0000000000000286 R12: 0000000000000800
R13: 00007fff46c5ca30 R14: 0000000000000004 R15: 0000000000020000
</TASK>
INFO: task syz-executor245:3538 blocked for more than 143 seconds.
Not tainted 5.15.156-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor245 state:D stack:24304 pid: 3538 ppid: 3533 flags:0x00004006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5030 [inline]
__schedule+0x12c4/0x45b0 kernel/sched/core.c:6376
schedule+0x11b/0x1f0 kernel/sched/core.c:6459
rwsem_down_write_slowpath+0xf0c/0x16a0 kernel/locking/rwsem.c:1165
inode_lock include/linux/fs.h:789 [inline]
lock_mount+0x21b/0x2c0 fs/namespace.c:2248
do_new_mount_fc fs/namespace.c:2942 [inline]
do_new_mount+0x433/0xb40 fs/namespace.c:3007
do_mount fs/namespace.c:3348 [inline]
__do_sys_mount fs/namespace.c:3556 [inline]
__se_sys_mount+0x2d5/0x3c0 fs/namespace.c:3533
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f34356fa26a
RSP: 002b:00007fff46c5c9d8 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fff46c5c9f0 RCX: 00007f34356fa26a
RDX: 0000000020001500 RSI: 0000000020000140 RDI: 00007fff46c5c9f0
RBP: 0000000000000005 R08: 00007fff46c5ca30 R09: 00000000000014f8
R10: 0000000000000800 R11: 0000000000000286 R12: 0000000000000800
R13: 00007fff46c5ca30 R14: 0000000000000004 R15: 0000000000020000
</TASK>
INFO: task syz-executor245:3539 blocked for more than 144 seconds.
Not tainted 5.15.156-syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor245 state:D stack:24960 pid: 3539 ppid: 3532 flags:0x00004006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5030 [inline]
__schedule+0x12c4/0x45b0 kernel/sched/core.c:6376
schedule+0x11b/0x1f0 kernel/sched/core.c:6459
rwsem_down_write_slowpath+0xf0c/0x16a0 kernel/locking/rwsem.c:1165
inode_lock include/linux/fs.h:789 [inline]
lock_mount+0x62/0x2c0 fs/namespace.c:2248
do_new_mount_fc fs/namespace.c:2942 [inline]
do_new_mount+0x433/0xb40 fs/namespace.c:3007
do_mount fs/namespace.c:3348 [inline]
__do_sys_mount fs/namespace.c:3556 [inline]
__se_sys_mount+0x2d5/0x3c0 fs/namespace.c:3533
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f34356fa26a
RSP: 002b:00007fff46c5c9d8 EFLAGS: 00000286 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fff46c5c9f0 RCX: 00007f34356fa26a
RDX: 0000000020001500 RSI: 0000000020000140 RDI: 00007fff46c5c9f0
RBP: 0000000000000005 R08: 00007fff46c5ca30 R09: 00000000000014f8
R10: 0000000000000800 R11: 0000000000000286 R12: 0000000000000800
R13: 00007fff46c5ca30 R14: 0000000000000004 R15: 0000000000020000
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/27:
#0: ffffffff8c91fb20 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
2 locks held by getty/3263:
#0: ffff888024765098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
#1: ffffc90002bab2e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6af/0x1db0 drivers/tty/n_tty.c:2158
1 lock held by syz-executor245/3534:
#0: ffff8880712102b0 (&sb->s_type->i_mutex_key#15){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:789 [inline]
#0: ffff8880712102b0 (&sb->s_type->i_mutex_key#15){+.+.}-{3:3}, at: lock_mount+0x62/0x2c0 fs/namespace.c:2248
1 lock held by syz-executor245/3535:
#0: ffff8880712102b0 (&sb->s_type->i_mutex_key#15){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:789 [inline]
#0: ffff8880712102b0 (&sb->s_type->i_mutex_key#15){+.+.}-{3:3}, at: lock_mount+0x21b/0x2c0 fs/namespace.c:2248
3 locks held by syz-executor245/3536:
1 lock held by syz-executor245/3538:
#0: ffff8880712102b0 (&sb->s_type->i_mutex_key#15){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:789 [inline]
#0: ffff8880712102b0 (&sb->s_type->i_mutex_key#15){+.+.}-{3:3}, at: lock_mount+0x21b/0x2c0 fs/namespace.c:2248
1 lock held by syz-executor245/3539:
#0: ffff8880712102b0 (&sb->s_type->i_mutex_key#15){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:789 [inline]
#0: ffff8880712102b0 (&sb->s_type->i_mutex_key#15){+.+.}-{3:3}, at: lock_mount+0x62/0x2c0 fs/namespace.c:2248

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

NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted 5.15.156-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x1e3/0x2d0 lib/dump_stack.c:106
nmi_cpu_backtrace+0x46a/0x4a0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x181/0x2a0 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:210 [inline]
watchdog+0xe72/0xeb0 kernel/hung_task.c:295
kthread+0x3f6/0x4f0 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:300
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 3536 Comm: syz-executor245 Not tainted 5.15.156-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
RIP: 0010:lock_is_held_type+0x122/0x180 kernel/locking/lockdep.c:5668
Code: e8 83 11 00 00 b8 ff ff ff ff 65 0f c1 05 f6 d7 e4 75 83 f8 01 75 40 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 <75> 46 41 f7 c4 00 02 00 00 74 01 fb 65 48 8b 04 25 28 00 00 00 48
RSP: 0018:ffffc90002c17478 EFLAGS: 00000046
RAX: 0000000000000001 RBX: 0000000000000003 RCX: ffff888078758000
RDX: 0000000000000000 RSI: ffffffff8a8b3c20 RDI: ffffffff8ad8f380
RBP: 0000000000000000 R08: ffffffff81ac4b6e R09: fffff9400037f0c9
R10: 0000000000000000 R11: dffffc0000000001 R12: 0000000000000246
R13: ffff888078758000 R14: 00000000ffffffff R15: ffffffff8c91faa0
FS: 0000555555950380(0000) GS:ffff8880b9b00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000564cf2431600 CR3: 000000001ae7f000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<NMI>
</NMI>
<TASK>
lock_is_held include/linux/lockdep.h:287 [inline]
___might_sleep+0xf1/0x6a0 kernel/sched/core.c:9592
__getblk_gfp+0x43/0xaf0 fs/buffer.c:1334
__bread_gfp+0x2a/0x390 fs/buffer.c:1381
sb_bread include/linux/buffer_head.h:337 [inline]
exfat_get_dentry+0x678/0x970 fs/exfat/dir.c:741
exfat_readdir fs/exfat/dir.c:122 [inline]
exfat_iterate+0xc09/0x34a0 fs/exfat/dir.c:258
iterate_dir+0x224/0x570
__do_sys_getdents64 fs/readdir.c:369 [inline]
__se_sys_getdents64+0x209/0x4f0 fs/readdir.c:354
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x3b/0xb0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f34356f8ed9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 17 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fff46c5cb68 EFLAGS: 00000246 ORIG_RAX: 00000000000000d9
RAX: ffffffffffffffda RBX: 00007f3435742095 RCX: 00007f34356f8ed9
RDX: 00000000000000ca RSI: 00000000200001c0 RDI: 0000000000000005
RBP: 0030656c69662f2e R08: 0000555555951378 R09: 0000555555951378
R10: 00000000000014f8 R11: 0000000000000246 R12: 0000000000000001
R13: 00007fff46c5cba0 R14: 00007fff46c5cb8c R15: 00007f343574203b
</TASK>
INFO: NMI handler (nmi_cpu_backtrace_handler) took too long to run: 1.346 msecs


---
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