[syzbot] [bcachefs?] INFO: task hung in chown_common (6)

From: syzbot
Date: Thu Mar 27 2025 - 03:28:15 EST

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Hello,

syzbot found the following issue on:

HEAD commit: 183601b78a9b Merge tag 'perf-urgent-2025-03-22' of git://g..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15ab73b0580000
kernel config: https://syzkaller.appspot.com/x/.config?x=620facf12ff15d10
dashboard link: https://syzkaller.appspot.com/bug?extid=389a7212df1c1578006b
compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e77793f17fc6/disk-183601b7.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/2cd0002d51f0/vmlinux-183601b7.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8e3a49885711/bzImage-183601b7.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+389a7212df1c1578006b@xxxxxxxxxxxxxxxxxxxxxxxxx

INFO: task syz.4.27:6087 blocked for more than 143 seconds.
Not tainted 6.14.0-rc7-syzkaller-00202-g183601b78a9b #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.27 state:D stack:27392 pid:6087 tgid:6052 ppid:5842 task_flags:0x400040 flags:0x00000004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5378 [inline]
__schedule+0x18bc/0x4c40 kernel/sched/core.c:6765
__schedule_loop kernel/sched/core.c:6842 [inline]
schedule+0x14b/0x320 kernel/sched/core.c:6857
schedule_preempt_disabled+0x13/0x30 kernel/sched/core.c:6914
rwsem_down_write_slowpath+0xeee/0x13b0 kernel/locking/rwsem.c:1176
__down_write_common kernel/locking/rwsem.c:1304 [inline]
__down_write kernel/locking/rwsem.c:1313 [inline]
down_write+0x1d7/0x220 kernel/locking/rwsem.c:1578
inode_lock include/linux/fs.h:877 [inline]
chown_common+0x3e1/0x850 fs/open.c:772
vfs_fchown fs/open.c:850 [inline]
ksys_fchown+0xe2/0x150 fs/open.c:862
__do_sys_fchown fs/open.c:867 [inline]
__se_sys_fchown fs/open.c:865 [inline]
__x64_sys_fchown+0x7a/0x90 fs/open.c:865
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f3a5638d169
RSP: 002b:00007f3a541d5038 EFLAGS: 00000246 ORIG_RAX: 000000000000005d
RAX: ffffffffffffffda RBX: 00007f3a565a6080 RCX: 00007f3a5638d169
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000004
RBP: 00007f3a5640e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f3a565a6080 R15: 00007fff6de31378
</TASK>

Showing all locks held in the system:
3 locks held by kworker/u8:1/13:
#0: ffff88814cbf3948 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3213 [inline]
#0: ffff88814cbf3948 ((wq_completion)ipv6_addrconf){+.+.}-{0:0}, at: process_scheduled_works+0x98b/0x18e0 kernel/workqueue.c:3319
#1: ffffc90000127c60 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline]
#1: ffffc90000127c60 ((work_completion)(&(&ifa->dad_work)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9c6/0x18e0 kernel/workqueue.c:3319
#2: ffffffff8fec3c48 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_net_lock include/linux/rtnetlink.h:129 [inline]
#2: ffffffff8fec3c48 (rtnl_mutex){+.+.}-{4:4}, at: addrconf_dad_work+0x10e/0x16a0 net/ipv6/addrconf.c:4190
1 lock held by khungtaskd/31:
#0: ffffffff8eb393e0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
#0: ffffffff8eb393e0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
#0: ffffffff8eb393e0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x55/0x2a0 kernel/locking/lockdep.c:6746
6 locks held by kworker/u8:3/53:
#0: ffff88801bef3948 ((wq_completion)netns){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3213 [inline]
#0: ffff88801bef3948 ((wq_completion)netns){+.+.}-{0:0}, at: process_scheduled_works+0x98b/0x18e0 kernel/workqueue.c:3319
#1: ffffc90000bd7c60 (net_cleanup_work){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline]
#1: ffffc90000bd7c60 (net_cleanup_work){+.+.}-{0:0}, at: process_scheduled_works+0x9c6/0x18e0 kernel/workqueue.c:3319
#2: ffffffff8feb7410 (pernet_ops_rwsem){++++}-{4:4}, at: cleanup_net+0x17a/0xd60 net/core/net_namespace.c:606
#3: ffff88807cd8d0e8 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:1030 [inline]
#3: ffff88807cd8d0e8 (&dev->mutex){....}-{4:4}, at: devl_dev_lock net/devlink/devl_internal.h:108 [inline]
#3: ffff88807cd8d0e8 (&dev->mutex){....}-{4:4}, at: devlink_pernet_pre_exit+0x13b/0x440 net/devlink/core.c:506
#4: ffff888027a4c250 (&devlink->lock_key#12){+.+.}-{4:4}, at: devl_lock net/devlink/core.c:276 [inline]
#4: ffff888027a4c250 (&devlink->lock_key#12){+.+.}-{4:4}, at: devl_dev_lock net/devlink/devl_internal.h:109 [inline]
#4: ffff888027a4c250 (&devlink->lock_key#12){+.+.}-{4:4}, at: devlink_pernet_pre_exit+0x14d/0x440 net/devlink/core.c:506
#5: ffffffff8fec3c48 (rtnl_mutex){+.+.}-{4:4}, at: nsim_destroy+0xa4/0x620 drivers/net/netdevsim/netdev.c:1016
2 locks held by getty/5582:
#0: ffff8880359ba0a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x25/0x70 drivers/tty/tty_ldisc.c:243
#1: ffffc90002fde2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x616/0x1770 drivers/tty/n_tty.c:2211
3 locks held by kworker/0:6/5923:
#0: ffff88801b080d48 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3213 [inline]
#0: ffff88801b080d48 ((wq_completion)events){+.+.}-{0:0}, at: process_scheduled_works+0x98b/0x18e0 kernel/workqueue.c:3319
#1: ffffc900044bfc60 ((work_completion)(&(&devlink->rwork)->work)){+.+.}-{0:0}, at: process_one_work kernel/workqueue.c:3214 [inline]
#1: ffffc900044bfc60 ((work_completion)(&(&devlink->rwork)->work)){+.+.}-{0:0}, at: process_scheduled_works+0x9c6/0x18e0 kernel/workqueue.c:3319
#2: ffffffff8eb3e8b8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:302 [inline]
#2: ffffffff8eb3e8b8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x381/0x820 kernel/rcu/tree_exp.h:996
5 locks held by syz.4.27/6053:
#0: ffff888031d3e420 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write+0x3f/0x90 fs/namespace.c:547
#1: ffff88805c0008e0 (&sb->s_type->i_mutex_key#20/1){+.+.}-{4:4}, at: inode_lock_nested include/linux/fs.h:912 [inline]
#1: ffff88805c0008e0 (&sb->s_type->i_mutex_key#20/1){+.+.}-{4:4}, at: filename_create+0x260/0x540 fs/namei.c:4082
#2: ffff88805c000cc8 (&inode->ei_update_lock){+.+.}-{4:4}, at: __bch2_create+0x355/0xf40 fs/bcachefs/fs.c:550
#3: ffff88805d084378 (&c->btree_trans_barrier){.+.+}-{0:0}, at: srcu_lock_acquire include/linux/srcu.h:164 [inline]
#3: ffff88805d084378 (&c->btree_trans_barrier){.+.+}-{0:0}, at: srcu_read_lock include/linux/srcu.h:256 [inline]
#3: ffff88805d084378 (&c->btree_trans_barrier){.+.+}-{0:0}, at: __bch2_trans_get+0x7e4/0xd30 fs/bcachefs/btree_iter.c:3408
#4: ffff88805d0a66d0 (&c->gc_lock){.+.+}-{4:4}, at: bch2_btree_update_start+0x680/0x1540 fs/bcachefs/btree_update_interior.c:1182
2 locks held by syz.4.27/6087:
#0: ffff888031d3e420 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write_file+0x5e/0x200 fs/namespace.c:591
#1: ffff88805c0008e0 (&sb->s_type->i_mutex_key#20){++++}-{4:4}, at: inode_lock include/linux/fs.h:877 [inline]
#1: ffff88805c0008e0 (&sb->s_type->i_mutex_key#20){++++}-{4:4}, at: chown_common+0x3e1/0x850 fs/open.c:772
3 locks held by kworker/u8:9/7839:
1 lock held by syz-executor/8812:
#0: ffff88802a39a0e0 (&type->s_umount_key#68){++++}-{4:4}, at: __super_lock fs/super.c:56 [inline]
#0: ffff88802a39a0e0 (&type->s_umount_key#68){++++}-{4:4}, at: __super_lock_excl fs/super.c:71 [inline]
#0: ffff88802a39a0e0 (&type->s_umount_key#68){++++}-{4:4}, at: deactivate_super+0xb5/0xf0 fs/super.c:505
2 locks held by syz-executor/9086:
#0: ffffffff8fec3c48 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_lock net/core/rtnetlink.c:79 [inline]
#0: ffffffff8fec3c48 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_nets_lock net/core/rtnetlink.c:335 [inline]
#0: ffffffff8fec3c48 (rtnl_mutex){+.+.}-{4:4}, at: rtnl_newlink+0xc55/0x1d30 net/core/rtnetlink.c:4021
#1: ffffffff8eb3e8b8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: exp_funnel_lock kernel/rcu/tree_exp.h:334 [inline]
#1: ffffffff8eb3e8b8 (rcu_state.exp_mutex){+.+.}-{4:4}, at: synchronize_rcu_expedited+0x451/0x820 kernel/rcu/tree_exp.h:996

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

NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 31 Comm: khungtaskd Not tainted 6.14.0-rc7-syzkaller-00202-g183601b78a9b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x241/0x360 lib/dump_stack.c:120
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:162 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:236 [inline]
watchdog+0x1058/0x10a0 kernel/hung_task.c:399
kthread+0x7a9/0x920 kernel/kthread.c:464
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
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 UID: 0 PID: 3445 Comm: kworker/u8:7 Not tainted 6.14.0-rc7-syzkaller-00202-g183601b78a9b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Workqueue: bat_events batadv_nc_worker
RIP: 0010:__lock_acquire+0xcbf/0x2100 kernel/locking/lockdep.c:5201
Code: bf 00 00 00 00 00 fc ff df 48 0f a3 1d da 92 b4 12 0f 83 66 09 00 00 49 8d 9d e0 0a 00 00 48 89 d8 48 c1 e8 03 48 89 44 24 58 <80> 3c 38 00 74 12 48 89 df e8 63 b2 89 00 48 bf 00 00 00 00 00 fc
RSP: 0018:ffffc9000c607850 EFLAGS: 00000806
RAX: 1ffff1100633315c RBX: ffff888031998ae0 RCX: ffffffff819ce554
RDX: 0000000000000000 RSI: 0000000000000008 RDI: dffffc0000000000
RBP: ffff888031998b40 R08: ffffffff94517847 R09: 1ffffffff28a2f08
R10: dffffc0000000000 R11: fffffbfff28a2f09 R12: ffff888031998ad4
R13: ffff888031998000 R14: 0000000000000000 R15: ffff888031998b60
FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00005577a2694950 CR3: 00000000350ae000 CR4: 00000000003526f0
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:5851
rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
rcu_read_lock include/linux/rcupdate.h:849 [inline]
batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:408 [inline]
batadv_nc_worker+0xec/0x610 net/batman-adv/network-coding.c:719
process_one_work kernel/workqueue.c:3238 [inline]
process_scheduled_works+0xabe/0x18e0 kernel/workqueue.c:3319
worker_thread+0x870/0xd30 kernel/workqueue.c:3400
kthread+0x7a9/0x920 kernel/kthread.c:464
ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:148
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
</TASK>

---
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Next message: tip-bot2 for Boqun Feng: "[tip: locking/urgent] locking/lockdep: Decrease nr_unused_locks if lock unused in zap_class()"
Previous message: syzbot: "Re: [syzbot] [bcachefs?] KMSAN: uninit-value in bch2_extent_crc_append (2)"
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