syzbot


INFO: task hung in cgroup_can_fork (2)

Status: upstream: reported on 2025/09/11 03:23
Reported-by: syzbot+6b5cbd79e0efb0612e59@syzkaller.appspotmail.com
First crash: 3d04h, last: 3d04h
Similar bugs (4)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream INFO: task hung in cgroup_can_fork (2) cgroups 1 5 358d 438d 0/29 auto-obsoleted due to no activity on 2024/12/20 05:36
linux-6.1 INFO: task hung in cgroup_can_fork 1 1 326d 326d 0/3 auto-obsoleted due to no activity on 2025/01/30 16:24
linux-5.15 INFO: task hung in cgroup_can_fork 1 1 344d 344d 0/3 auto-obsoleted due to no activity on 2025/01/13 02:23
upstream INFO: task hung in cgroup_can_fork cgroups 1 C error error 6 1340d 1361d 0/29 auto-obsoleted due to no activity on 2023/09/02 21:24

Sample crash report:
INFO: task kthreadd:2 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:kthreadd        state:D stack:27304 pid:    2 ppid:     0 flags:0x00004000
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
 percpu_rwsem_wait+0x2d8/0x310 kernel/locking/percpu-rwsem.c:160
 __percpu_down_read+0xc9/0x100 kernel/locking/percpu-rwsem.c:174
 percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
 cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:724 [inline]
 cgroup_css_set_fork kernel/cgroup/cgroup.c:6196 [inline]
 cgroup_can_fork+0xc94/0xda0 kernel/cgroup/cgroup.c:6314
 copy_process+0x2290/0x3e00 kernel/fork.c:2382
 kernel_clone+0x219/0x930 kernel/fork.c:2679
 kernel_thread+0xc8/0x120 kernel/fork.c:2731
 create_kthread kernel/kthread.c:357 [inline]
 kthreadd+0x520/0x6f0 kernel/kthread.c:703
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:287
 </TASK>
INFO: task dhcpcd:3854 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:dhcpcd          state:D stack:21376 pid: 3854 ppid:  3853 flags:0x00004002
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
 percpu_rwsem_wait+0x2d8/0x310 kernel/locking/percpu-rwsem.c:160
 __percpu_down_read+0xc9/0x100 kernel/locking/percpu-rwsem.c:174
 percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
 cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:724 [inline]
 cgroup_css_set_fork kernel/cgroup/cgroup.c:6196 [inline]
 cgroup_can_fork+0xc94/0xda0 kernel/cgroup/cgroup.c:6314
 copy_process+0x2290/0x3e00 kernel/fork.c:2382
 kernel_clone+0x219/0x930 kernel/fork.c:2679
 __do_sys_clone kernel/fork.c:2796 [inline]
 __se_sys_clone kernel/fork.c:2780 [inline]
 __x64_sys_clone+0x170/0x1c0 kernel/fork.c:2780
 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: 0033:0x7f13e9e6b636
RSP: 002b:00007ffc9d92aeb0 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007ffc9d92aeb8 RCX: 00007f13e9e6b636
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007ffc9d94b400 R08: 0000000000000000 R09: 0000000000000001
R10: 00007f13e9d97a10 R11: 0000000000000246 R12: 00007ffc9d92aff0
R13: 0000000000000000 R14: 0000000000000000 R15: 000055a3c1391ac0
 </TASK>
INFO: task syz-executor:4182 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:18344 pid: 4182 ppid:  4177 flags:0x00004000
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
 rwsem_down_write_slowpath+0xc46/0x11f0 kernel/locking/rwsem.c:1165
 inode_lock_nested include/linux/fs.h:822 [inline]
 filename_create+0x1f2/0x450 fs/namei.c:3835
 do_mkdirat+0x9d/0x5a0 fs/namei.c:4080
 __do_sys_mkdirat fs/namei.c:4105 [inline]
 __se_sys_mkdirat fs/namei.c:4103 [inline]
 __x64_sys_mkdirat+0x85/0x90 fs/namei.c:4103
 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: 0033:0x7f91a04e7417
RSP: 002b:00007ffd39713de8 EFLAGS: 00000206 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007ffd39713e40 RCX: 00007f91a04e7417
RDX: 00000000000001ff RSI: 00007ffd39713e40 RDI: 00000000ffffff9c
RBP: 0000000000000001 R08: 0000000000000017 R09: 00007ffd39713b37
R10: 0000000000000000 R11: 0000000000000206 R12: 0000000000000008
R13: 0000000000000003 R14: 0000000000000009 R15: 0000000000000000
 </TASK>
INFO: task syz-executor:4183 blocked for more than 144 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:21536 pid: 4183 ppid:  4179 flags:0x00004000
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
 rwsem_down_write_slowpath+0xc46/0x11f0 kernel/locking/rwsem.c:1165
 mmap_write_lock include/linux/mmap_lock.h:71 [inline]
 mpol_rebind_mm+0x33/0x2c0 mm/mempolicy.c:381
 cpuset_attach+0x330/0x5f0 kernel/cgroup/cpuset.c:2376
 cgroup_migrate_execute+0x7eb/0x1010 kernel/cgroup/cgroup.c:2574
 cgroup_attach_task+0x562/0x7e0 kernel/cgroup/cgroup.c:2869
 __cgroup1_procs_write+0x2e5/0x3f0 kernel/cgroup/cgroup-v1.c:527
 cgroup_file_write+0x2f7/0x630 kernel/cgroup/cgroup.c:3943
 kernfs_fop_write_iter+0x379/0x4c0 fs/kernfs/file.c:296
 call_write_iter include/linux/fs.h:2172 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x712/0xd00 fs/read_write.c:594
 ksys_write+0x14d/0x250 fs/read_write.c:647
 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: 0033:0x7fbef5b1065f
RSP: 002b:00007ffc8340d420 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fbef5b1065f
RDX: 0000000000000001 RSI: 00007ffc8340d470 RDI: 0000000000000003
RBP: 00007ffc8340d9e0 R08: 0000000000000000 R09: 00007ffc8340d277
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001
R13: 00007ffc8340d470 R14: 00007ffc8340d9a0 R15: 00007ffc8340d9e0
 </TASK>
INFO: task syz-executor:4189 blocked for more than 144 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:20104 pid: 4189 ppid:  4181 flags:0x00004000
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
 rwsem_down_write_slowpath+0xc46/0x11f0 kernel/locking/rwsem.c:1165
 inode_lock_nested include/linux/fs.h:822 [inline]
 filename_create+0x1f2/0x450 fs/namei.c:3835
 do_mkdirat+0x9d/0x5a0 fs/namei.c:4080
 __do_sys_mkdirat fs/namei.c:4105 [inline]
 __se_sys_mkdirat fs/namei.c:4103 [inline]
 __x64_sys_mkdirat+0x85/0x90 fs/namei.c:4103
 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: 0033:0x7fdc73261417
RSP: 002b:00007ffe0ec0fe98 EFLAGS: 00000202 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007ffe0ec0fef0 RCX: 00007fdc73261417
RDX: 00000000000001ff RSI: 00007ffe0ec0fef0 RDI: 00000000ffffff9c
RBP: 0000000000000001 R08: 0000000000000017 R09: 00007ffe0ec0fbe7
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000008
R13: 0000000000000003 R14: 0000000000000009 R15: 0000000000000000
 </TASK>
INFO: task syz-executor:4196 blocked for more than 144 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:19560 pid: 4196 ppid:  4178 flags:0x00004000
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
 cgroup_kn_lock_live+0xee/0x230 kernel/cgroup/cgroup.c:1639
 cgroup_mkdir+0xaf/0xe60 kernel/cgroup/cgroup.c:5556
 kernfs_iop_mkdir+0x24c/0x3d0 fs/kernfs/dir.c:1175
 vfs_mkdir+0x387/0x570 fs/namei.c:4065
 do_mkdirat+0x1d7/0x5a0 fs/namei.c:4090
 __do_sys_mkdirat fs/namei.c:4105 [inline]
 __se_sys_mkdirat fs/namei.c:4103 [inline]
 __x64_sys_mkdirat+0x85/0x90 fs/namei.c:4103
 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: 0033:0x7fce1806a417
RSP: 002b:00007ffec40a2668 EFLAGS: 00000202 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007ffec40a26c0 RCX: 00007fce1806a417
RDX: 00000000000001ff RSI: 00007ffec40a26c0 RDI: 00000000ffffff9c
RBP: 0000000000000001 R08: 0000000000000017 R09: 00007ffec40a23b7
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000008
R13: 0000000000000003 R14: 0000000000000009 R15: 0000000000000000
 </TASK>
INFO: task syz.3.6:4296 blocked for more than 144 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.6         state:D stack:25800 pid: 4296 ppid:  4192 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
 percpu_rwsem_wait+0x2d8/0x310 kernel/locking/percpu-rwsem.c:160
 __percpu_down_read+0xc9/0x100 kernel/locking/percpu-rwsem.c:174
 percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
 cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:724 [inline]
 exit_signals+0x3e5/0x510 kernel/signal.c:2991
 do_exit+0x256/0x20a0 kernel/exit.c:830
 do_group_exit+0x12e/0x300 kernel/exit.c:997
 get_signal+0x6ca/0x12c0 kernel/signal.c:2900
 arch_do_signal_or_restart+0xc1/0x1300 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fe424cfebe3
RSP: 002b:00007ffcb9a9ed78 EFLAGS: 00000246 ORIG_RAX: 0000000000000009
RAX: fffffffffffffffc RBX: 00007fe4237676c0 RCX: 00007fe424cfebe3
RDX: 0000000000000000 RSI: 0000000000021000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 00000000ffffffff R09: 0000000000000000
R10: 0000000000020022 R11: 0000000000000246 R12: 00007ffcb9a9eed0
R13: ffffffffffffffc0 R14: 0000000000001000 R15: 0000000000000000
 </TASK>
INFO: task syz.3.6:4297 blocked for more than 145 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.3.6         state:D stack:24072 pid: 4297 ppid:  4192 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
 percpu_rwsem_wait+0x2d8/0x310 kernel/locking/percpu-rwsem.c:160
 __percpu_down_read+0xc9/0x100 kernel/locking/percpu-rwsem.c:174
 percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
 cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:724 [inline]
 exit_signals+0x3e5/0x510 kernel/signal.c:2991
 do_exit+0x256/0x20a0 kernel/exit.c:830
 do_group_exit+0x12e/0x300 kernel/exit.c:997
 get_signal+0x6ca/0x12c0 kernel/signal.c:2900
 arch_do_signal_or_restart+0xc1/0x1300 arch/x86/kernel/signal.c:867
 handle_signal_work kernel/entry/common.c:154 [inline]
 exit_to_user_mode_loop+0x9e/0x130 kernel/entry/common.c:178
 exit_to_user_mode_prepare+0xb1/0x140 kernel/entry/common.c:214
 __syscall_exit_to_user_mode_work kernel/entry/common.c:296 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:307
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fe424cfeba9
RSP: 002b:00007fe422f660e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007fe424f45fa8 RCX: 00007fe424cfeba9
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007fe424f45fa8
RBP: 00007fe424f45fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fe424f46038 R14: 00007ffcb9a9ecf0 R15: 00007ffcb9a9edd8
 </TASK>

Showing all locks held in the system:
1 lock held by kthreadd/2:
 #0: ffffffff8c141ef0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: copy_process+0x2290/0x3e00 kernel/fork.c:2382
1 lock held by khungtaskd/27:
 #0: ffffffff8c11c460 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x0/0x30
no locks held by klogd/3550.
2 locks held by udevd/3561:
 #0: ffffffff8c1a64f0 (dup_mmap_sem){.+.+}-{0:0}, at: dup_mmap kernel/fork.c:503 [inline]
 #0: ffffffff8c1a64f0 (dup_mmap_sem){.+.+}-{0:0}, at: dup_mm kernel/fork.c:1466 [inline]
 #0: ffffffff8c1a64f0 (dup_mmap_sem){.+.+}-{0:0}, at: copy_mm+0x21f/0x1380 kernel/fork.c:1518
 #1: ffff88802c3bf828 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
 #1: ffff88802c3bf828 (&mm->mmap_lock){++++}-{3:3}, at: dup_mmap kernel/fork.c:504 [inline]
 #1: ffff88802c3bf828 (&mm->mmap_lock){++++}-{3:3}, at: dup_mm kernel/fork.c:1466 [inline]
 #1: ffff88802c3bf828 (&mm->mmap_lock){++++}-{3:3}, at: copy_mm+0x238/0x1380 kernel/fork.c:1518
1 lock held by dhcpcd/3854:
 #0: ffffffff8c141ef0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: copy_process+0x2290/0x3e00 kernel/fork.c:2382
2 locks held by getty/3949:
 #0: ffff88814cd64098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:252
 #1: ffffc90002cf62e8 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x5ba/0x1a30 drivers/tty/n_tty.c:2158
1 lock held by udevd/4174:
 #0: ffff888079fcf828 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
 #0: ffff888079fcf828 (&mm->mmap_lock){++++}-{3:3}, at: __vm_munmap+0xf3/0x230 mm/mmap.c:2949
1 lock held by udevd/4176:
 #0: ffff88807ab20128 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
 #0: ffff88807ab20128 (&mm->mmap_lock){++++}-{3:3}, at: __vm_munmap+0xf3/0x230 mm/mmap.c:2949
1 lock held by syz-executor/4180:
 #0: ffffffff8c141ef0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x256/0x20a0 kernel/exit.c:830
2 locks held by syz-executor/4182:
 #0: ffff88807a7a6460 (sb_writers#10){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:377
 #1: ffff8880757d9590 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:822 [inline]
 #1: ffff8880757d9590 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: filename_create+0x1f2/0x450 fs/namei.c:3835
7 locks held by syz-executor/4183:
 #0: ffff88807c782460 (sb_writers#11){.+.+}-{0:0}, at: vfs_write+0x28a/0xd00 fs/read_write.c:590
 #1: ffff88802b3a2488 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e5/0x4c0 fs/kernfs/file.c:287
 #2: ffffffff8c141d08 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_kn_lock_live+0xee/0x230 kernel/cgroup/cgroup.c:1639
 #3: ffffffff8bfbabd0 (cpu_hotplug_lock){++++}-{0:0}, at: cgroup_attach_lock kernel/cgroup/cgroup.c:2388 [inline]
 #3: ffffffff8bfbabd0 (cpu_hotplug_lock){++++}-{0:0}, at: cgroup_procs_write_start+0x17c/0x580 kernel/cgroup/cgroup.c:2898
 #4: ffffffff8c141ef0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: cgroup_attach_lock kernel/cgroup/cgroup.c:2390 [inline]
 #4: ffffffff8c141ef0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: cgroup_procs_write_start+0x192/0x580 kernel/cgroup/cgroup.c:2898
 #5: ffffffff8c14f748 (cpuset_mutex){+.+.}-{3:3}, at: cpuset_attach+0xac/0x5f0 kernel/cgroup/cpuset.c:2348
 #6: ffff88807b105c28 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock include/linux/mmap_lock.h:71 [inline]
 #6: ffff88807b105c28 (&mm->mmap_lock){++++}-{3:3}, at: mpol_rebind_mm+0x33/0x2c0 mm/mempolicy.c:381
2 locks held by syz-executor/4189:
 #0: ffff88807a7a6460 (sb_writers#10){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:377
 #1: ffff8880757d9590 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:822 [inline]
 #1: ffff8880757d9590 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: filename_create+0x1f2/0x450 fs/namei.c:3835
3 locks held by syz-executor/4196:
 #0: ffff88807a7a6460 (sb_writers#10){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:377
 #1: ffff8880757d9590 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: inode_lock_nested include/linux/fs.h:822 [inline]
 #1: ffff8880757d9590 (&type->i_mutex_dir_key#6/1){+.+.}-{3:3}, at: filename_create+0x1f2/0x450 fs/namei.c:3835
 #2: ffffffff8c141d08 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_kn_lock_live+0xee/0x230 kernel/cgroup/cgroup.c:1639
1 lock held by udevd/4198:
 #0: ffff88807b106a28 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock_killable include/linux/mmap_lock.h:87 [inline]
 #0: ffff88807b106a28 (&mm->mmap_lock){++++}-{3:3}, at: __vm_munmap+0xf3/0x230 mm/mmap.c:2949
1 lock held by syz.3.6/4296:
 #0: ffffffff8c141ef0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x256/0x20a0 kernel/exit.c:830
1 lock held by syz.3.6/4297:
 #0: ffffffff8c141ef0 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x256/0x20a0 kernel/exit.c:830

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

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 07/12/2025
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: 9 Comm: kworker/u4:0 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: bat_events batadv_nc_worker
RIP: 0010:check_preemption_disabled+0x60/0x110 lib/smp_processor_id.c:19
Code: 00 48 3b 4c 24 08 0f 85 c4 00 00 00 48 83 c4 10 5b 41 5e 41 5f 5d c3 48 c7 04 24 00 00 00 00 9c 8f 04 24 f7 04 24 00 02 00 00 <74> cc 65 4c 8b 3d e6 70 59 76 41 f6 47 2f 04 74 0a 41 83 bf 10 04
RSP: 0018:ffffc90000ce7a88 EFLAGS: 00000046
RAX: 0000000000000001 RBX: ffff88813fed0000 RCX: 0000000080000000
RDX: 0000000000000000 RSI: ffffffff8a0b2420 RDI: ffffffff8a59a240
RBP: ffffc90000ce7bd0 R08: dffffc0000000000 R09: fffffbfff1ad31e6
R10: fffffbfff1ad31e6 R11: 1ffffffff1ad31e5 R12: 000000000000004f
R13: dffffc0000000000 R14: ffff88813fed0aec R15: 1ffff9200019cf64
FS:  0000000000000000(0000) GS:ffff8880b9100000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffcb9a9eff8 CR3: 000000007e117000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 lockdep_recursion_inc kernel/locking/lockdep.c:431 [inline]
 lock_release+0x156/0x870 kernel/locking/lockdep.c:5642
 rcu_read_unlock include/linux/rcupdate.h:772 [inline]
 batadv_nc_purge_orig_hash net/batman-adv/network-coding.c:416 [inline]
 batadv_nc_worker+0x25b/0x5c0 net/batman-adv/network-coding.c:723
 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>

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/09/11 03:22 linux-5.15.y de9476bb4f1b fdeaa69b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan-perf INFO: task hung in cgroup_can_fork
* Struck through repros no longer work on HEAD.