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Message-ID: <67e05e30.050a0220.21942d.0003.GAE@google.com>
Date: Sun, 23 Mar 2025 12:17:04 -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.0.17:6724 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:24768 pid:6724 tgid:6722 ppid:6593 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: 0033:0x7fce81f8d169
RSP: 002b:00007fce82d75038 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fce821a5fa0 RCX: 00007fce81f8d169
RDX: 0000000000007fec RSI: 0000400000000540 RDI: 0000000000000007
RBP: 00007fce8200e2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fce821a5fa0 R15: 00007ffc98f4b948
</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/u8:3/56:
#0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
#1: ffffc9000121fd80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
2 locks held by kworker/u8:4/81:
#0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
#1: ffffc9000217fd80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
2 locks held by kworker/u8:5/1317:
#0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
#1: ffffc90004897d80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
2 locks held by kworker/u8:6/3513:
#0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
#1: ffffc9000cadfd80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
2 locks held by kworker/u8:7/3805:
#0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
#1: ffffc9000d66fd80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
2 locks held by getty/5580:
#0: ffff88803216c0a0 (&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.0.17/6724:
#0: ffff8880227fd438 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
#1: ffff88807965c420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
#2: ffff8880749e0148 (&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.1.19/6772:
#0: ffff888028adf438 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
#1: ffff88802984c420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
#2: ffff888074838148 (&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.2.21/6792:
#0: ffff888034b1bcf8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
#1: ffff88805ffda420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
#2: ffff8880748387b8 (&sb->s_type->i_mutex_key#20){++++}-{4:4}, at: netfs_start_io_direct+0x116/0x260 fs/netfs/locking.c:188
2 locks held by kworker/u8:8/6807:
#0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
#1: ffffc90003157d80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
3 locks held by syz.3.23/6812:
#0: ffff88807c3c70b8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
#1: ffff888026990420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
#2: ffff888074838e28 (&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.4.25/6838:
#0: ffff8880794df438 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
#1: ffff88807c934420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
#2: ffff8880749e07b8 (&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.5.27/6864:
#0: ffff8880248b07f8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
#1: ffff88805ccc4420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
#2: ffff888074839498 (&sb->s_type->i_mutex_key#20){++++}-{4:4}, at: netfs_start_io_direct+0x116/0x260 fs/netfs/locking.c:188
2 locks held by kworker/u8:11/6865:
#0: ffff88801b081148 ((wq_completion)events_unbound){+.+.}-{0:0}, at: process_one_work+0x1293/0x1ba0 kernel/workqueue.c:3204
#1: ffffc90003117d80 ((work_completion)(&rreq->work)){+.+.}-{0:0}, at: process_one_work+0x921/0x1ba0 kernel/workqueue.c:3205
3 locks held by syz.6.29/6891:
#0: ffff8880355f7eb8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
#1: ffff888078eb2420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
#2: ffff888074839b08 (&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.7.31/6917:
#0: ffff88807f33f0b8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
#1: ffff88807613e420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
#2: ffff88807483a178 (&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.8.34/6953:
#0: ffff88806f5b4478 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
#1: ffff888078710420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
#2: ffff88807483ae58 (&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.9.36/6980:
#0: ffff888029c18ef8 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x267/0x390 fs/file.c:1191
#1: ffff888033c44420 (sb_writers#14){.+.+}-{0:0}, at: ksys_write+0x12b/0x250 fs/read_write.c:731
#2: ffff88807483b4c8 (&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 0
CPU: 0 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 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 6813 Comm: kworker/u8:9 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_unbound nsim_dev_trap_report_work
RIP: 0010:orc_ip arch/x86/kernel/unwind_orc.c:80 [inline]
RIP: 0010:__orc_find+0x70/0xf0 arch/x86/kernel/unwind_orc.c:102
Code: ec 72 4e 4c 89 e2 48 29 ea 48 89 d6 48 c1 ea 3f 48 c1 fe 02 48 01 f2 48 d1 fa 48 8d 5c 95 00 48 89 da 48 c1 ea 03 0f b6 34 0a <48> 89 da 83 e2 07 83 c2 03 40 38 f2 7c 05 40 84 f6 75 4b 48 63 13
RSP: 0018:ffffc900031476d8 EFLAGS: 00000a06
RAX: ffffffff90f0214a RBX: ffffffff906e9fd0 RCX: dffffc0000000000
RDX: 1ffffffff20dd3fa RSI: 0000000000000000 RDI: ffffffff906e9fa8
RBP: ffffffff906e9fd0 R08: ffffffff90f0218c R09: ffffffff90f117cc
R10: ffffc900031477d8 R11: 0000000000004070 R12: ffffffff906e9fd0
R13: ffffffff814070f3 R14: ffffffff906e9fa8 R15: ffffffff906e9fcc
FS: 0000000000000000(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000c008cfd000 CR3: 000000000df7e000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<NMI>
</NMI>
<TASK>
orc_find arch/x86/kernel/unwind_orc.c:227 [inline]
unwind_next_frame+0x2be/0x20c0 arch/x86/kernel/unwind_orc.c:494
__unwind_start+0x45f/0x7f0 arch/x86/kernel/unwind_orc.c:760
unwind_start arch/x86/include/asm/unwind.h:64 [inline]
arch_stack_walk+0x74/0x100 arch/x86/kernel/stacktrace.c:24
stack_trace_save+0x95/0xd0 kernel/stacktrace.c:122
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:582
poison_slab_object mm/kasan/common.c:247 [inline]
__kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2338 [inline]
slab_free mm/slub.c:4598 [inline]
kmem_cache_free+0x152/0x4c0 mm/slub.c:4700
kfree_skbmem+0x1a4/0x1f0 net/core/skbuff.c:1148
__kfree_skb net/core/skbuff.c:1205 [inline]
consume_skb net/core/skbuff.c:1436 [inline]
consume_skb+0xcc/0x100 net/core/skbuff.c:1430
nsim_dev_trap_report drivers/net/netdevsim/dev.c:821 [inline]
nsim_dev_trap_report_work+0x8cf/0xd00 drivers/net/netdevsim/dev.c:851
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=169ac43f980000
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=17803c4c580000
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