[v5.15] INFO: task hung in relay_open

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 29e53a5b1c4f Linux 5.15.194
git tree: linux-5.15.y
console output: https://syzkaller.appspot.com/x/log.txt?x=17d53092580000
kernel config: https://syzkaller.appspot.com/x/.config?x=e1bb6d24ef2164eb
dashboard link: https://syzkaller.appspot.com/bug?extid=15c8dc72bf96fc2731ed
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/8cd4e3ff852c/disk-29e53a5b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/21e1f773622c/vmlinux-29e53a5b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/8f418c0a25cc/bzImage-29e53a5b.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+15c8dc...@syzkaller.appspotmail.com

INFO: task syz.4.39:4503 blocked for more than 143 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.39 state:D stack:26752 pid: 4503 ppid: 4190 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6537
__mutex_lock_common+0xc71/0x2390 kernel/locking/mutex.c:669
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
relay_open+0x314/0x8e0 kernel/relay.c:518
do_blk_trace_setup+0x559/0x9d0 kernel/trace/blktrace.c:559
__blk_trace_setup kernel/trace/blktrace.c:599 [inline]
blk_trace_ioctl+0x404/0x4f0 kernel/trace/blktrace.c:740
blkdev_ioctl+0x153/0x690 block/ioctl.c:593
block_ioctl+0xac/0xf0 block/fops.c:496
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f446040eec9
RSP: 002b:00007f445e655038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f4460666090 RCX: 00007f446040eec9
RDX: 00002000000004c0 RSI: 00000000c0481273 RDI: 0000000000000006
RBP: 00007f4460491f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4460666128 R14: 00007f4460666090 R15: 00007ffe86d149c8
</TASK>
INFO: task syz.4.39:4504 blocked for more than 144 seconds.
Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.4.39 state:D stack:28256 pid: 4504 ppid: 4190 flags:0x00004004
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5049 [inline]
__schedule+0x11bb/0x4390 kernel/sched/core.c:6395
schedule+0x11b/0x1e0 kernel/sched/core.c:6478
schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6537
__mutex_lock_common+0xc71/0x2390 kernel/locking/mutex.c:669
__mutex_lock kernel/locking/mutex.c:729 [inline]
mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
blk_trace_ioctl+0x108/0x4f0 kernel/trace/blktrace.c:735
blkdev_common_ioctl+0xfbe/0x1c70 block/ioctl.c:532
blkdev_ioctl+0x295/0x690 block/ioctl.c:598
block_ioctl+0xac/0xf0 block/fops.c:496
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:874 [inline]
__se_sys_ioctl+0xfa/0x170 fs/ioctl.c:860
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7f446040eec9
RSP: 002b:00007f445e634038 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 00007f4460666180 RCX: 00007f446040eec9
RDX: 0000000000000000 RSI: 0000000000001276 RDI: 0000000000000006
RBP: 00007f4460491f91 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f4460666218 R14: 00007f4460666180 R15: 00007ffe86d149c8
</TASK>

Showing all locks held in the system:
1 lock held by khungtaskd/27:
#0: ffffffff8c11c660 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
2 locks held by getty/3958:
#0: ffff88814cedb098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
#1: ffffc90002d032e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x5ba/0x1a30 drivers/tty/n_tty.c:2158
2 locks held by kworker/u4:10/4352:
2 locks held by syz.2.38/4492:
2 locks held by syz.4.39/4503:
#0: ffff8880201b0608 (&q->debugfs_mutex){+.+.}-{3:3}, at: blk_trace_ioctl+0x108/0x4f0 kernel/trace/blktrace.c:735
#1: ffffffff8c15ad68 (relay_channels_mutex){+.+.}-{3:3}, at: relay_open+0x314/0x8e0 kernel/relay.c:518
1 lock held by syz.4.39/4504:
#0: ffff8880201b0608 (&q->debugfs_mutex){+.+.}-{3:3}, at: blk_trace_ioctl+0x108/0x4f0 kernel/trace/blktrace.c:735
3 locks held by kworker/u4:18/4888:

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

NMI backtrace for cpu 0
CPU: 0 PID: 27 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Call Trace:
<TASK>
dump_stack_lvl+0x168/0x230 lib/dump_stack.c:106
nmi_cpu_backtrace+0x397/0x3d0 lib/nmi_backtrace.c:111
nmi_trigger_cpumask_backtrace+0x163/0x280 lib/nmi_backtrace.c:62
trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:212 [inline]
watchdog+0xe0f/0xe50 kernel/hung_task.c:369
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 4348 Comm: kworker/u4:8 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/18/2025
Workqueue: phy10 ieee80211_iface_work
RIP: 0010:kfree+0x191/0x2a0 mm/slub.c:4565
Code: 0f 85 26 01 00 00 48 8d 4a 08 65 48 0f c7 0f 0f 94 c0 a8 01 74 a8 65 48 8b 04 25 28 00 00 00 48 3b 44 24 20 0f 85 8b 00 00 00 <48> 83 c4 28 5b 41 5c 41 5d 41 5e 41 5f 5d c3 0f 0b e9 92 fe ff ff
RSP: 0018:ffffc900035ff800 EFLAGS: 00000246
RAX: 678e25cca4b5c500 RBX: ffff88807a5a7000 RCX: 678e25cca4b5c500
RDX: dffffc0000000000 RSI: ffffffff8a0b1820 RDI: ffffffff8a59a4c0
RBP: ffffc900035ff990 R08: dffffc0000000000 R09: fffffbfff1ff7a26
R10: fffffbfff1ff7a26 R11: 1ffffffff1ff7a25 R12: ffff888016841dc0
R13: 0000000000000001 R14: ffffffff8931cf2e R15: ffffea0001e96800
FS: 0000000000000000(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000002000 CR3: 00000001a1405000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
ieee80211_bss_info_update+0x86e/0xaa0 net/mac80211/scan.c:232
ieee80211_rx_bss_info net/mac80211/ibss.c:1123 [inline]
ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1614 [inline]
ieee80211_ibss_rx_queued_mgmt+0x16d0/0x29c0 net/mac80211/ibss.c:1643
ieee80211_iface_process_skb net/mac80211/iface.c:1459 [inline]
ieee80211_iface_work+0x70e/0xc60 net/mac80211/iface.c:1513
process_one_work+0x863/0x1000 kernel/workqueue.c:2310
worker_thread+0xaa8/0x12a0 kernel/workqueue.c:2457
kthread+0x436/0x520 kernel/kthread.c:334
ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
</TASK>
vkms_vblank_simulate: vblank timer overrun


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