[moderation] [fs?] INFO: task hung in do_unlinkat (5)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 448b3fe5a0ea Merge tag 'hwmon-for-v6.9-rc8' of git://git.k..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14bf03c0980000
kernel config: https://syzkaller.appspot.com/x/.config?x=9d7ea7de0cb32587
dashboard link: https://syzkaller.appspot.com/bug?extid=ebe1a8166b3417e37772
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
CC: [adilger...@dilger.ca linux...@vger.kernel.org linux-...@vger.kernel.org linux-...@vger.kernel.org ty...@mit.edu]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ccbdd58c1f3e/disk-448b3fe5.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6786079c3170/vmlinux-448b3fe5.xz
kernel image: https://storage.googleapis.com/syzbot-assets/496bdcf3d703/bzImage-448b3fe5.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ebe1a8...@syzkaller.appspotmail.com

INFO: task syz-executor.2:7620 blocked for more than 143 seconds.
Not tainted 6.9.0-rc7-syzkaller-00117-g448b3fe5a0ea #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor.2 state:D stack:28304 pid:7620 tgid:7615 ppid:5087 flags:0x00000006
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5409 [inline]
__schedule+0x1796/0x4a00 kernel/sched/core.c:6746
__schedule_loop kernel/sched/core.c:6823 [inline]
schedule+0x14b/0x320 kernel/sched/core.c:6838
schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6895
rwsem_down_write_slowpath+0xeeb/0x13b0 kernel/locking/rwsem.c:1178
__down_write_common+0x1af/0x200 kernel/locking/rwsem.c:1306
inode_lock_nested include/linux/fs.h:830 [inline]
do_unlinkat+0x26a/0x830 fs/namei.c:4386
__do_sys_unlink fs/namei.c:4447 [inline]
__se_sys_unlink fs/namei.c:4445 [inline]
__x64_sys_unlink+0x49/0x60 fs/namei.c:4445
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f82c807dd69
RSP: 002b:00007f82c8df90c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000057
RAX: ffffffffffffffda RBX: 00007f82c81ac050 RCX: 00007f82c807dd69
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000020000440
RBP: 00007f82c80ca49e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007f82c81ac050 R15: 00007ffd08ffa438
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/29:
#0: ffffffff8e334da0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:329 [inline]
#0: ffffffff8e334da0 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:781 [inline]
#0: ffffffff8e334da0 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x55/0x2a0 kernel/locking/lockdep.c:6614
2 locks held by getty/4832:
#0: ffff88802acac0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc900031332f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x6b5/0x1e10 drivers/tty/n_tty.c:2201
2 locks held by syz-executor.2/7616:
2 locks held by syz-executor.2/7620:
#0: ffff8880637ac420 (sb_writers#34){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:409
#1: ffff8880773e8188 (&type->i_mutex_dir_key#28/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:830 [inline]
#1: ffff8880773e8188 (&type->i_mutex_dir_key#28/1){+.+.}-{3:3}, at: do_unlinkat+0x26a/0x830 fs/namei.c:4386
1 lock held by syz-executor.4/9139:
#0: ffffffff8e33a138 (rcu_state.exp_mutex){+.+.}-{3:3}, at: exp_funnel_lock kernel/rcu/tree_exp.h:291 [inline]
#0: ffffffff8e33a138 (rcu_state.exp_mutex){+.+.}-{3:3}, at: synchronize_rcu_expedited+0x39a/0x820 kernel/rcu/tree_exp.h:939
4 locks held by syz-executor.2/9561:
#0: ffff888030446420 (sb_writers#4){.+.+}-{0:0}, at: mnt_want_write_file+0x61/0x200 fs/namespace.c:453
#1: ffff88807724e800 (&sb->s_type->i_mutex_key#7){++++}-{3:3}, at: inode_lock include/linux/fs.h:795 [inline]
#1: ffff88807724e800 (&sb->s_type->i_mutex_key#7){++++}-{3:3}, at: vfs_fileattr_set+0x139/0xd50 fs/ioctl.c:682
#2: ffff88807724e9a0 (mapping.invalidate_lock){++++}-{3:3}, at: filemap_invalidate_lock include/linux/fs.h:840 [inline]
#2: ffff88807724e9a0 (mapping.invalidate_lock){++++}-{3:3}, at: ext4_change_inode_journal_flag+0x10e/0x840 fs/ext4/inode.c:5981
#3: ffff888030450b98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_writepages_down_write fs/ext4/ext4.h:1781 [inline]
#3: ffff888030450b98 (&sbi->s_writepages_rwsem){++++}-{0:0}, at: ext4_change_inode_journal_flag+0x19e/0x840 fs/ext4/inode.c:5989
1 lock held by syz-executor.3/9563:
#0: ffff88804e2da0e0 (&type->s_umount_key#27/1){+.+.}-{3:3}, at: alloc_super+0x221/0x9d0 fs/super.c:343

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

NMI backtrace for cpu 0
CPU: 0 PID: 29 Comm: khungtaskd Not tainted 6.9.0-rc7-syzkaller-00117-g448b3fe5a0ea #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:114
nmi_cpu_backtrace+0x49c/0x4d0 lib/nmi_backtrace.c:113
nmi_trigger_cpumask_backtrace+0x198/0x320 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:160 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:223 [inline]
watchdog+0xfde/0x1020 kernel/hung_task.c:380
kthread+0x2f0/0x390 kernel/kthread.c:388
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4527 Comm: udevd Not tainted 6.9.0-rc7-syzkaller-00117-g448b3fe5a0ea #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/02/2024
RIP: 0010:check_wait_context kernel/locking/lockdep.c:4787 [inline]
RIP: 0010:__lock_acquire+0x6ee/0x1fd0 kernel/locking/lockdep.c:5087
Code: 0f 85 a0 11 00 00 41 f6 47 01 80 0f 85 21 04 00 00 84 db 40 0f b6 c5 0f b6 cb 0f 44 c8 89 4c 24 5c 48 8b 44 24 40 0f b6 04 10 <84> c0 0f 85 1f 13 00 00 48 8b 04 24 8b 28 41 89 ec ff cd 0f 88 a5
RSP: 0018:ffffc900039df910 EFLAGS: 00000046
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000002
RDX: dffffc0000000000 RSI: ffff88807c688ad8 RDI: ffffffff92efe500
RBP: 0000000000000002 R08: ffffffff92efe507 R09: 1ffffffff25dfca0
R10: dffffc0000000000 R11: fffffbfff25dfca1 R12: 0000000000000001
R13: ffff88807c688000 R14: 1ffff1100f8d115f R15: ffff88807c688af8
FS: 00007f04a4d17c80(0000) GS:ffff8880b9500000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f3719cd66e4 CR3: 000000002e174000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<NMI>
</NMI>
<TASK>
lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5754
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0xd5/0x120 kernel/locking/spinlock.c:162
__debug_check_no_obj_freed lib/debugobjects.c:978 [inline]
debug_check_no_obj_freed+0x234/0x580 lib/debugobjects.c:1019
slab_free_hook mm/slub.c:2078 [inline]
slab_free mm/slub.c:4286 [inline]
kmem_cache_free+0xd5/0x2d0 mm/slub.c:4350
user_path_at_empty+0x4c/0x60 fs/namei.c:2923
do_readlinkat+0x118/0x3b0 fs/stat.c:499
__do_sys_readlink fs/stat.c:532 [inline]
__se_sys_readlink fs/stat.c:529 [inline]
__x64_sys_readlink+0x7f/0x90 fs/stat.c:529
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f04a4917d47
Code: 73 01 c3 48 8b 0d e1 90 0d 00 f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 59 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d b1 90 0d 00 f7 d8 64 89 01 48
RSP: 002b:00007fff6bfd9078 EFLAGS: 00000246 ORIG_RAX: 0000000000000059
RAX: ffffffffffffffda RBX: 00007fff6bfd9088 RCX: 00007f04a4917d47
RDX: 0000000000000400 RSI: 00007fff6bfd9088 RDI: 00007fff6bfd9568
RBP: 0000000000000400 R08: 000055c76f6a4a54 R09: 0000000000000000
R10: 0000000000000812 R11: 0000000000000246 R12: 00007fff6bfd9568
R13: 00007fff6bfd94d8 R14: 000055c76f690910 R15: 0000000000000000
</TASK>


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[syzbot]

Sending this report to the next reporting stage.