From: syzbot <syzbot+4e415f7013e8d1af362b@syzkaller.appspotmail.com>
To: cgroups@vger.kernel.org, hannes@cmpxchg.org,
linux-kernel@vger.kernel.org, mkoutny@suse.com,
syzkaller-bugs@googlegroups.com, tj@kernel.org
Subject: [syzbot] [cgroups?] INFO: task hung in cgroup1_get_tree
Date: Thu, 25 Jun 2026 22:10:44 -0700 [thread overview]
Message-ID: <6a3e09d4.ac7367b4.6675.0003.GAE@google.com> (raw)
Hello,
syzbot found the following issue on:
HEAD commit: ab9de95c9cf9 Merge tag 'rust-7.2-2' of git://git.kernel.or..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13976591580000
kernel config: https://syzkaller.appspot.com/x/.config?x=77808e35144e725c
dashboard link: https://syzkaller.appspot.com/bug?extid=4e415f7013e8d1af362b
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/ea216d6c635b/disk-ab9de95c.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a4726046a068/vmlinux-ab9de95c.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1ee56b4f63b2/bzImage-ab9de95c.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+4e415f7013e8d1af362b@syzkaller.appspotmail.com
INFO: task syz.3.5067:25142 blocked for more than 143 seconds.
Tainted: G L syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.5067 state:D stack:27688 pid:25142 tgid:25139 ppid:24491 task_flags:0x400140 flags:0x00080002
Call Trace:
<TASK>
context_switch kernel/sched/core.c:5504 [inline]
__schedule+0x125c/0x6730 kernel/sched/core.c:7228
__schedule_loop kernel/sched/core.c:7307 [inline]
schedule+0xdd/0x390 kernel/sched/core.c:7322
cgroup_lock_and_drain_offline+0x383/0x800 kernel/cgroup/cgroup.c:3275
cgroup1_get_tree+0xc2/0x1620 kernel/cgroup/cgroup-v1.c:1265
vfs_get_tree+0x92/0x320 fs/super.c:1694
fc_mount fs/namespace.c:1198 [inline]
do_new_mount_fc fs/namespace.c:3765 [inline]
do_new_mount fs/namespace.c:3841 [inline]
path_mount+0x7d0/0x23d0 fs/namespace.c:4161
do_mount fs/namespace.c:4174 [inline]
__do_sys_mount fs/namespace.c:4390 [inline]
__se_sys_mount fs/namespace.c:4367 [inline]
__x64_sys_mount+0x293/0x310 fs/namespace.c:4367
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x115/0x870 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fe24299ce59
RSP: 002b:00007fe243858028 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fe242c16090 RCX: 00007fe24299ce59
RDX: 0000200000000080 RSI: 0000200000001180 RDI: 0000000000000000
RBP: 00007fe242a32e6f R08: 0000200000000000 R09: 0000000000000000
R10: 0000000000004000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe242c16128 R14: 00007fe242c16090 R15: 00007ffc1d1628c8
</TASK>
Showing all locks held in the system:
1 lock held by khungtaskd/31:
#0: ffffffff8e7e60c0 (rcu_read_lock){....}-{1:3}, at: rcu_lock_acquire include/linux/rcupdate.h:300 [inline]
#0: ffffffff8e7e60c0 (rcu_read_lock){....}-{1:3}, at: rcu_read_lock include/linux/rcupdate.h:840 [inline]
#0: ffffffff8e7e60c0 (rcu_read_lock){....}-{1:3}, at: debug_show_all_locks+0x3d/0x184 kernel/locking/lockdep.c:6775
6 locks held by kworker/1:6/5718:
#0: ffff8880202ea940 ((wq_completion)usb_hub_wq){+.+.}-{0:0}, at: process_one_work+0x12b1/0x1940 kernel/workqueue.c:3297
#1: ffffc900040d7d08 ((work_completion)(&hub->events)){+.+.}-{0:0}, at: process_one_work+0x988/0x1940 kernel/workqueue.c:3298
#2: ffff88802ac581d8 (&dev->mutex){....}-{4:4}, at: device_lock include/linux/device.h:1102 [inline]
#2: ffff88802ac581d8 (&dev->mutex){....}-{4:4}, at: hub_event+0x1bd/0x4af0 drivers/usb/core/hub.c:5899
#3: ffff88802ad59568 (&port_dev->status_lock){+.+.}-{4:4}, at: usb_lock_port drivers/usb/core/hub.c:3252 [inline]
#3: ffff88802ad59568 (&port_dev->status_lock){+.+.}-{4:4}, at: hub_port_connect drivers/usb/core/hub.c:5464 [inline]
#3: ffff88802ad59568 (&port_dev->status_lock){+.+.}-{4:4}, at: hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
#3: ffff88802ad59568 (&port_dev->status_lock){+.+.}-{4:4}, at: port_event drivers/usb/core/hub.c:5871 [inline]
#3: ffff88802ad59568 (&port_dev->status_lock){+.+.}-{4:4}, at: hub_event+0x2bd2/0x4af0 drivers/usb/core/hub.c:5953
#4: ffff88802ac76760 (hcd->address0_mutex){+.+.}-{4:4}, at: hub_port_connect drivers/usb/core/hub.c:5465 [inline]
#4: ffff88802ac76760 (hcd->address0_mutex){+.+.}-{4:4}, at: hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
#4: ffff88802ac76760 (hcd->address0_mutex){+.+.}-{4:4}, at: port_event drivers/usb/core/hub.c:5871 [inline]
#4: ffff88802ac76760 (hcd->address0_mutex){+.+.}-{4:4}, at: hub_event+0x2bfb/0x4af0 drivers/usb/core/hub.c:5953
#5: ffffffff8fbf2c48 (ehci_cf_port_reset_rwsem){.+.+}-{4:4}, at: hub_port_reset+0x1a5/0x1c60 drivers/usb/core/hub.c:3067
2 locks held by getty/13406:
#0: ffff8880383d10a0 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x24/0x80 drivers/tty/tty_ldisc.c:243
#1: ffffc9000202e2e8 (&ldata->atomic_read_lock){+.+.}-{4:4}, at: n_tty_read+0x419/0x14e0 drivers/tty/n_tty.c:2211
1 lock held by syz.2.5163/25788:
#0: ffff88807d22e0d8 (&type->s_umount_key#64){++++}-{4:4}, at: do_remount fs/namespace.c:3404 [inline]
#0: ffff88807d22e0d8 (&type->s_umount_key#64){++++}-{4:4}, at: path_mount+0x1757/0x23d0 fs/namespace.c:4153
1 lock held by syz.0.5462/27160:
=============================================
NMI backtrace for cpu 1
CPU: 1 UID: 0 PID: 31 Comm: khungtaskd Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
nmi_cpu_backtrace.cold+0x12d/0x151 lib/nmi_backtrace.c:122
nmi_trigger_cpumask_backtrace+0x21c/0x2a0 lib/nmi_backtrace.c:65
trigger_all_cpu_backtrace include/linux/nmi.h:162 [inline]
__sys_info lib/sys_info.c:157 [inline]
sys_info+0x141/0x190 lib/sys_info.c:165
check_hung_uninterruptible_tasks kernel/hung_task.c:353 [inline]
watchdog+0xcb1/0x1030 kernel/hung_task.c:561
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
Sending NMI from CPU 1 to CPUs 0:
NMI backtrace for cpu 0
CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/09/2026
RIP: 0010:pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:64
Code: d6 85 02 c3 cc cc cc cc 0f 1f 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 66 90 0f 00 2d 23 28 10 00 fb f4 <e9> fc 48 03 00 66 2e 0f 1f 84 00 00 00 00 00 66 90 90 90 90 90 90
RSP: 0018:ffffffff8e407e10 EFLAGS: 00000246
RAX: 00000000088c3e3f RBX: ffffffff8e491480 RCX: ffffffff8b9b72d5
RDX: 0000000000000000 RSI: ffffffff8df596ca RDI: ffffffff8c1e7180
RBP: fffffbfff1c92290 R08: 0000000000000001 R09: ffffed101708678d
R10: ffff8880b8433c6b R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 1ffffffff1c80fc6 R15: dffffc0000000000
FS: 0000000000000000(0000) GS:ffff8881242e7000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007fa09d875d58 CR3: 000000004c22a000 CR4: 00000000003526f0
DR0: 0000000000000008 DR1: 0000000000000007 DR2: 0000000000000004
DR3: 0000000000000008 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
arch_safe_halt arch/x86/include/asm/paravirt.h:62 [inline]
default_idle+0x9/0x10 arch/x86/kernel/process.c:768
default_idle_call+0x6c/0xb0 kernel/sched/idle.c:122
cpuidle_idle_call kernel/sched/idle.c:199 [inline]
do_idle+0x3a7/0x5b0 kernel/sched/idle.c:355
cpu_startup_entry+0x4f/0x60 kernel/sched/idle.c:454
rest_init+0x251/0x260 init/main.c:717
start_kernel+0x48e/0x490 init/main.c:1175
x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
x86_64_start_kernel+0x12b/0x130 arch/x86/kernel/head64.c:291
common_startup_64+0x13e/0x158
</TASK>
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.
syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title
If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)
If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report
If you want to undo deduplication, reply with:
#syz undup
reply other threads:[~2026-06-26 5:10 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=6a3e09d4.ac7367b4.6675.0003.GAE@google.com \
--to=syzbot+4e415f7013e8d1af362b@syzkaller.appspotmail.com \
--cc=cgroups@vger.kernel.org \
--cc=hannes@cmpxchg.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mkoutny@suse.com \
--cc=syzkaller-bugs@googlegroups.com \
--cc=tj@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox