Message-ID: <67e07258.050a0220.21942d.0007.GAE@google.com>
Date: Sun, 23 Mar 2025 13:43:04 -0700
From: syzbot <syzbot+62262fdc0e01d99573fc@...kaller.appspotmail.com>
To: brauner@...nel.org, dhowells@...hat.com, jack@...e.cz, jlayton@...nel.org, 
	kprateek.nayak@....com, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, mjguzik@...il.com, netfs@...ts.linux.dev, 
	oleg@...hat.com, swapnil.sapkal@....com, syzkaller-bugs@...glegroups.com, 
	viro@...iv.linux.org.uk
Subject: Re: [syzbot] [netfs?] INFO: task hung in netfs_unbuffered_write_iter

Hello,

syzbot has tested the proposed patch but the reproducer is still triggering an issue:
INFO: task hung in netfs_unbuffered_write_iter

INFO: task syz.0.17:6690 blocked for more than 143 seconds.
      Not tainted 6.13.0-rc1-syzkaller-00017-gaaec5a95d596-dirty #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.17        state:D stack:25184 pid:6690  tgid:6689  ppid:6491   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5369 [inline]
 __schedule+0xe58/0x5ad0 kernel/sched/core.c:6756
 __schedule_loop kernel/sched/core.c:6833 [inline]
 schedule+0xe7/0x350 kernel/sched/core.c:6848
 bit_wait+0x15/0xe0 kernel/sched/wait_bit.c:237
 __wait_on_bit+0x62/0x180 kernel/sched/wait_bit.c:49
 out_of_line_wait_on_bit+0xda/0x110 kernel/sched/wait_bit.c:64
 wait_on_bit include/linux/wait_bit.h:77 [inline]
 netfs_unbuffered_write_iter_locked+0xba8/0xe70 fs/netfs/direct_write.c:105
 netfs_unbuffered_write_iter+0x413/0x6d0 fs/netfs/direct_write.c:193
 v9fs_file_write_iter+0xbf/0x100 fs/9p/vfs_file.c:404
 new_sync_write fs/read_write.c:586 [inline]
 vfs_write+0x5ae/0x1150 fs/read_write.c:679
 ksys_write+0x12b/0x250 fs/read_write.c:731
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fbba998d169
RSP: 002b:00007fbba97f9038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fbba9ba5fa0 RCX: 00007fbba998d169
RDX: 0000000000007fec RSI: 0000400000000540 RDI: 0000000000000007
RBP: 00007fbba9a0e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fbba9ba5fa0 R15: 00007ffea301fe68
 </TASK>

Showing all locks held in the system:
2 locks held by kworker/u8:0/11:
 #0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
 #1: ffffc90000107d80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
2 locks held by kworker/u8:1/12:
 #0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
 #1: ffffc90000117d80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
1 lock held by khungtaskd/30:
 #0: ffffffff8e1bac80 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
 #0: ffffffff8e1bac80 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffffffff8e1bac80 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x7f/0x390 kernel/locking/lockdep.c:6744
2 locks held by kworker/u8:2/35:
 #0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
 #1: ffffc90000ab7d80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
2 locks held by kworker/u8:4/80:
 #0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
 #1: ffffc9000213fd80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
3 locks held by kworker/u8:6/2887:
2 locks held by kworker/u8:7/2936:
 #0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
 #1: ffffc9000bc87d80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
2 locks held by kworker/u8:8/3460:
 #0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
 #1: ffffc9000c917d80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
2 locks held by kworker/u8:9/3519:
 #0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
 #1: ffffc9000c757d80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
2 locks held by kworker/u8:10/3600:
 #0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
 #1: ffffc9000cbe7d80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
2 locks held by kworker/u8:11/3645:
 #0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
 #1: ffffc9000d047d80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
2 locks held by kworker/u8:12/3693:
 #0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
 #1: ffffc9000d437d80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
2 locks held by getty/5579:
 #0: ffff8880315940a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
 #1: ffffc90002fde2f0 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0xfba/0x1480 drivers/tty/n_tty.c:2211
3 locks held by syz.0.17/6690:
 #0: ffff88807c837eb8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
 #1: ffff88807341a420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
 #2: ffff8880739f0148 (&sb->s_type->i_mutex_key#20){++++}-{4:4}, at: netfs_start_io_direct+0x116/0x260 fs/netfs/locking.c:188
3 locks held by syz.1.19/6790:
 #0: ffff88802beef7b8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
 #1: ffff888055054420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
 #2: ffff8880739f07b8 (&sb->s_type->i_mutex_key#20){++++}-{4:4}, at: netfs_start_io_direct+0x116/0x260 fs/netfs/locking.c:188
3 locks held by syz.2.22/6813:
 #0: ffff888034a757b8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
 #1: ffff8880736a2420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
 #2: ffff8880739f0e28 (&sb->s_type->i_mutex_key#20){++++}-{4:4}, at: netfs_start_io_direct+0x116/0x260 fs/netfs/locking.c:188
3 locks held by syz.3.24/6832:
 #0: ffff88802fbce9b8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
 #1: ffff888030d96420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
 #2: ffff888073af0148 (&sb->s_type->i_mutex_key#20){++++}-{4:4}, at: netfs_start_io_direct+0x116/0x260 fs/netfs/locking.c:188
3 locks held by syz.4.26/6857:
 #0: ffff8880355be638 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
 #1: ffff8880331c0420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
 #2: ffff888073af07b8 (&sb->s_type->i_mutex_key#20){++++}-{4:4}, at: netfs_start_io_direct+0x116/0x260 fs/netfs/locking.c:188
3 locks held by syz.5.28/6882:
 #0: ffff8880635d1eb8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
 #1: ffff88807347c420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
 #2: ffff8880739f1498 (&sb->s_type->i_mutex_key#20){++++}-{4:4}, at: netfs_start_io_direct+0x116/0x260 fs/netfs/locking.c:188
3 locks held by syz.6.30/6910:
 #0: ffff88807b32e2b8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
 #1: ffff888029cb0420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
 #2: ffff8880739f1b08 (&sb->s_type->i_mutex_key#20){++++}-{4:4}, at: netfs_start_io_direct+0x116/0x260 fs/netfs/locking.c:188
3 locks held by syz.7.32/6938:
 #0: ffff88802fba9278 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
 #1: ffff88806225e420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
 #2: ffff888073af0e28 (&sb->s_type->i_mutex_key#20){++++}-{4:4}, at: netfs_start_io_direct+0x116/0x260 fs/netfs/locking.c:188
3 locks held by syz.8.34/6969:
 #0: ffff8880336ea478 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
 #1: ffff88802a7a4420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
 #2: ffff888073af1498 (&sb->s_type->i_mutex_key#20){++++}-{4:4}, at: netfs_start_io_direct+0x116/0x260 fs/netfs/locking.c:188
3 locks held by syz.9.36/6996:
 #0: ffff88801e2c27f8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
 #1: ffff88802d796420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
 #2: ffff8880739f2178 (&sb->s_type->i_mutex_key#20){++++}-{4:4}, at: netfs_start_io_direct+0x116/0x260 fs/netfs/locking.c:188

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

NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 30 Comm: khungtaskd Not tainted 6.13.0-rc1-syzkaller-00017-gaaec5a95d596-dirty #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+0x116/0x1f0 lib/dump_stack.c:120
 nmi_cpu_backtrace+0x27b/0x390 lib/nmi_backtrace.c:113
 nmi_trigger_cpumask_backtrace+0x29c/0x300 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:234 [inline]
 watchdog+0xf14/0x1240 kernel/hung_task.c:397
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 5871 Comm: kworker/0:4 Not tainted 6.13.0-rc1-syzkaller-00017-gaaec5a95d596-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
Workqueue: events_power_efficient gc_worker
RIP: 0010:__lock_acquire+0x2fe/0x3c40 kernel/locking/lockdep.c:5162
Code: 47 10 48 89 c2 48 89 44 24 50 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03 80 3c 02 00 0f 85 70 2b 00 00 49 8d 47 18 4d 89 67 10 <48> 89 c2 48 89 44 24 48 48 b8 00 00 00 00 00 fc ff df 48 c1 ea 03
RSP: 0018:ffffc90003ad7990 EFLAGS: 00000046
RAX: ffff8880315f53c8 RBX: 0000000000000000 RCX: 0000000000000002
RDX: 1ffff110062bea78 RSI: 1ffff110062bea75 RDI: ffff8880315f53b8
RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000001
R10: 000000000000000a R11: 0000000000000003 R12: ffffffff8e1bac80
R13: ffff8880315f4880 R14: 0000000000000021 R15: ffff8880315f53b0
FS:  0000000000000000(0000) GS:ffff8880b8600000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c008d0a000 CR3: 000000000df7e000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <NMI>
 </NMI>
 <TASK>
 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5849
 rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
 rcu_read_lock include/linux/rcupdate.h:849 [inline]
 gc_worker+0x24d/0x1760 net/netfilter/nf_conntrack_core.c:1532
 process_one_work+0x9c5/0x1ba0 kernel/workqueue.c:3229
 process_scheduled_works kernel/workqueue.c:3310 [inline]
 worker_thread+0x6c8/0xf00 kernel/workqueue.c:3391
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>


Tested on:

commit:         aaec5a95 pipe_read: don't wake up the writer if the pi..
git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
console output: https://syzkaller.appspot.com/x/log.txt?x=11550804580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=8d5a2956e94d7972
dashboard link: https://syzkaller.appspot.com/bug?extid=62262fdc0e01d99573fc
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=10e90804580000

Powered by blists - more mailing lists