syzbot


INFO: task hung in cgroup_can_fork (2)

Status: upstream: reported C repro on 2025/09/23 15:45
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+80596b0b7c6cb3fdc803@syzkaller.appspotmail.com
First crash: 112d, last: 4d00h
Fix bisection: the issue occurs on the latest tested release (bisect log)
  
Bug presence (1)
Date Name Commit Repro Result
2025/09/24 upstream (ToT) cec1e6e5d1ab C [report] INFO: task hung in exit_mmap
Similar bugs (5)
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 480d 560d 0/29 auto-obsoleted due to no activity on 2024/12/20 05:36
linux-5.15 INFO: task hung in cgroup_can_fork (2) origin:upstream 1 C 58 2d10h 125d 0/3 upstream: reported C repro on 2025/09/11 03:23
linux-6.1 INFO: task hung in cgroup_can_fork 1 1 448d 448d 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 466d 466d 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 1463d 1483d 0/29 auto-obsoleted due to no activity on 2023/09/02 21:24

Sample crash report:
INFO: task dhcpcd:3932 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:20960 pid:3932  ppid:3931   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 percpu_rwsem_wait+0x2bd/0x300 kernel/locking/percpu-rwsem.c:162
 __percpu_down_read+0xda/0x120 kernel/locking/percpu-rwsem.c:177
 percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
 cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:748 [inline]
 cgroup_css_set_fork kernel/cgroup/cgroup.c:6432 [inline]
 cgroup_can_fork+0xc27/0xd30 kernel/cgroup/cgroup.c:6565
 copy_process+0x248b/0x4020 kernel/fork.c:2446
 kernel_clone+0x225/0x8b0 kernel/fork.c:2757
 __do_sys_clone kernel/fork.c:2898 [inline]
 __se_sys_clone kernel/fork.c:2882 [inline]
 __x64_sys_clone+0x17c/0x1d0 kernel/fork.c:2882
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f9b16a04636
RSP: 002b:00007ffd4bec58b0 EFLAGS: 00000246 ORIG_RAX: 0000000000000038
RAX: ffffffffffffffda RBX: 00007ffd4bec58b8 RCX: 00007f9b16a04636
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000001200011
RBP: 00007ffd4bee5e00 R08: 0000000000000000 R09: 0000000000000001
R10: 00007f9b16930a10 R11: 0000000000000246 R12: 00007ffd4bec59f0
R13: 0000000000000000 R14: 0000000000000000 R15: 0000556bfd3dbac0
 </TASK>
INFO: task udevd:4307 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:udevd           state:D stack:25472 pid:4307  ppid:3636   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 percpu_rwsem_wait+0x2bd/0x300 kernel/locking/percpu-rwsem.c:162
 __percpu_down_read+0xda/0x120 kernel/locking/percpu-rwsem.c:177
 percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
 cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:748 [inline]
 exit_signals+0x3c0/0x4f0 kernel/signal.c:2963
 do_exit+0x578/0x2400 kernel/exit.c:827
 do_group_exit+0x217/0x2d0 kernel/exit.c:1022
 __do_sys_exit_group kernel/exit.c:1033 [inline]
 __se_sys_exit_group kernel/exit.c:1031 [inline]
 __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1031
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f97d28f16c5
RSP: 002b:00007fff2201b848 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 000055a425424220 RCX: 00007f97d28f16c5
RDX: 00000000000000e7 RSI: fffffffffffffe68 RDI: 0000000000000000
RBP: 000055a42541c910 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fff2201b890 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
INFO: task udevd:4377 blocked for more than 143 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:udevd           state:D stack:26560 pid:4377  ppid:3636   flags:0x00004002
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 percpu_rwsem_wait+0x2bd/0x300 kernel/locking/percpu-rwsem.c:162
 __percpu_down_read+0xda/0x120 kernel/locking/percpu-rwsem.c:177
 percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
 cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:748 [inline]
 exit_signals+0x3c0/0x4f0 kernel/signal.c:2963
 do_exit+0x578/0x2400 kernel/exit.c:827
 do_group_exit+0x217/0x2d0 kernel/exit.c:1022
 __do_sys_exit_group kernel/exit.c:1033 [inline]
 __se_sys_exit_group kernel/exit.c:1031 [inline]
 __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1031
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f97d28f16c5
RSP: 002b:00007fff2201b848 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 000055a425423cf0 RCX: 00007f97d28f16c5
RDX: 00000000000000e7 RSI: fffffffffffffe68 RDI: 0000000000000000
RBP: 000055a42541c910 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fff2201b890 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
INFO: task syz-executor:4393 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:24832 pid:4393  ppid:4294   flags:0x00004004
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 percpu_rwsem_wait+0x2bd/0x300 kernel/locking/percpu-rwsem.c:162
 __percpu_down_read+0xda/0x120 kernel/locking/percpu-rwsem.c:177
 percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
 cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:748 [inline]
 exit_signals+0x3c0/0x4f0 kernel/signal.c:2963
 do_exit+0x578/0x2400 kernel/exit.c:827
 do_group_exit+0x217/0x2d0 kernel/exit.c:1022
 get_signal+0x1272/0x1350 kernel/signal.c:2871
 arch_do_signal_or_restart+0xb7/0x1240 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f2407f85853
RSP: 002b:00007fff41e42e78 EFLAGS: 00000202 ORIG_RAX: 000000000000003d
RAX: fffffffffffffe00 RBX: 000000000000112f RCX: 00007f2407f85853
RDX: 0000000040000000 RSI: 00007fff41e42e8c RDI: 00000000ffffffff
RBP: 00007fff41e42e8c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000002
R13: 00007fff41e42ef8 R14: 00007fff41e43178 R15: 0000000000000000
 </TASK>
INFO: task syz-executor:4400 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:21216 pid:4400  ppid:4394   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6696
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x555/0xaf0 kernel/locking/mutex.c:747
 cgroup_lock include/linux/cgroup.h:442 [inline]
 cgroup_kn_lock_live+0xee/0x230 kernel/cgroup/cgroup.c:1700
 __cgroup_procs_write+0x73/0x350 kernel/cgroup/cgroup.c:5174
 cgroup_procs_write+0x23/0x40 kernel/cgroup/cgroup.c:5214
 cgroup_file_write+0x2f8/0x660 kernel/cgroup/cgroup.c:4100
 kernfs_fop_write_iter+0x3b2/0x520 fs/kernfs/file.c:352
 call_write_iter include/linux/fs.h:2265 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x44c/0x960 fs/read_write.c:584
 ksys_write+0x143/0x240 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fde29b8e1ff
RSP: 002b:00007ffc93a5e110 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fde29b8e1ff
RDX: 0000000000000001 RSI: 00007ffc93a5e160 RDI: 0000000000000003
RBP: 00007ffc93a5e6d0 R08: 0000000000000000 R09: 00007ffc93a5df67
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001
R13: 00007ffc93a5e160 R14: 00007ffc93a5e690 R15: 00007ffc93a5e6d0
 </TASK>
INFO: task syz-executor:4405 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:21480 pid:4405  ppid:4397   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 rwsem_down_write_slowpath+0xbed/0x1090 kernel/locking/rwsem.c:1189
 mmap_write_lock include/linux/mmap_lock.h:71 [inline]
 mpol_rebind_mm+0xbe/0x370 mm/mempolicy.c:386
 cpuset_attach+0x284/0x540 kernel/cgroup/cpuset.c:2663
 cgroup_migrate_execute+0x7a3/0xf30 kernel/cgroup/cgroup.c:2662
 cgroup_attach_task+0x558/0x840 kernel/cgroup/cgroup.c:2953
 __cgroup1_procs_write+0x2e0/0x3e0 kernel/cgroup/cgroup-v1.c:522
 cgroup_file_write+0x2f8/0x660 kernel/cgroup/cgroup.c:4100
 kernfs_fop_write_iter+0x3b2/0x520 fs/kernfs/file.c:352
 call_write_iter include/linux/fs.h:2265 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x44c/0x960 fs/read_write.c:584
 ksys_write+0x143/0x240 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f83da98e1ff
RSP: 002b:00007ffc1dc60830 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f83da98e1ff
RDX: 0000000000000001 RSI: 00007ffc1dc60880 RDI: 0000000000000003
RBP: 00007ffc1dc60df0 R08: 0000000000000000 R09: 00007ffc1dc60687
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001
R13: 00007ffc1dc60880 R14: 00007ffc1dc60db0 R15: 00007ffc1dc60df0
 </TASK>
INFO: task syz-executor:4406 blocked for more than 145 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor    state:D stack:21952 pid:4406  ppid:4398   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 schedule_preempt_disabled+0xf/0x20 kernel/sched/core.c:6696
 __mutex_lock_common kernel/locking/mutex.c:679 [inline]
 __mutex_lock+0x555/0xaf0 kernel/locking/mutex.c:747
 cgroup_lock include/linux/cgroup.h:442 [inline]
 cgroup_kn_lock_live+0xee/0x230 kernel/cgroup/cgroup.c:1700
 __cgroup_procs_write+0x73/0x350 kernel/cgroup/cgroup.c:5174
 cgroup_procs_write+0x23/0x40 kernel/cgroup/cgroup.c:5214
 cgroup_file_write+0x2f8/0x660 kernel/cgroup/cgroup.c:4100
 kernfs_fop_write_iter+0x3b2/0x520 fs/kernfs/file.c:352
 call_write_iter include/linux/fs.h:2265 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x44c/0x960 fs/read_write.c:584
 ksys_write+0x143/0x240 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f372098e1ff
RSP: 002b:00007ffd4040d1b0 EFLAGS: 00000293 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007f372098e1ff
RDX: 0000000000000001 RSI: 00007ffd4040d200 RDI: 0000000000000003
RBP: 00007ffd4040d770 R08: 0000000000000000 R09: 00007ffd4040d007
R10: 0000000000000000 R11: 0000000000000293 R12: 0000000000000001
R13: 00007ffd4040d200 R14: 00007ffd4040d730 R15: 00007ffd4040d770
 </TASK>
INFO: task syz.1.121:4725 blocked for more than 145 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.1.121       state:D stack:25696 pid:4725  ppid:4399   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 rwsem_down_write_slowpath+0xbed/0x1090 kernel/locking/rwsem.c:1189
 mmap_write_lock include/linux/mmap_lock.h:71 [inline]
 exit_mmap+0x20f/0x8e0 mm/mmap.c:3258
 __mmput+0x118/0x3c0 kernel/fork.c:1200
 exit_mm+0x1e6/0x2c0 kernel/exit.c:565
 do_exit+0x8c1/0x2400 kernel/exit.c:867
 do_group_exit+0x217/0x2d0 kernel/exit.c:1022
 __do_sys_exit_group kernel/exit.c:1033 [inline]
 __se_sys_exit_group kernel/exit.c:1031 [inline]
 __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1031
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f2407f8f749
RSP: 002b:00007fff41e42c88 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f2407f8f749
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007fff41e42cec R08: 0000000541e42d7f R09: 00000000000927c0
R10: 0000000000000001 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000000927c0 R14: 0000000000027754 R15: 00007fff41e42d40
 </TASK>
INFO: task syz.0.132:4745 blocked for more than 145 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.132       state:D stack:25696 pid:4745  ppid:4395   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 percpu_rwsem_wait+0x2bd/0x300 kernel/locking/percpu-rwsem.c:162
 __percpu_down_read+0xda/0x120 kernel/locking/percpu-rwsem.c:177
 percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
 cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:748 [inline]
 exit_signals+0x3c0/0x4f0 kernel/signal.c:2963
 do_exit+0x578/0x2400 kernel/exit.c:827
 do_group_exit+0x217/0x2d0 kernel/exit.c:1022
 __do_sys_exit_group kernel/exit.c:1033 [inline]
 __se_sys_exit_group kernel/exit.c:1031 [inline]
 __x64_sys_exit_group+0x3b/0x40 kernel/exit.c:1031
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f778958f749
RSP: 002b:00007ffeb3523de8 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f778958f749
RDX: 0000000000000064 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 00007ffeb3523e4c R08: 00000005b3523edf R09: 00000000000927c0
R10: 0000000000000001 R11: 0000000000000246 R12: 000000000000006e
R13: 00000000000927c0 R14: 0000000000027cd3 R15: 00007ffeb3523ea0
 </TASK>
INFO: task syz.0.132:4746 blocked for more than 145 seconds.
      Not tainted syzkaller #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz.0.132       state:D stack:25728 pid:4746  ppid:4395   flags:0x00004000
Call Trace:
 <TASK>
 context_switch kernel/sched/core.c:5244 [inline]
 __schedule+0x10ec/0x40b0 kernel/sched/core.c:6561
 schedule+0xb9/0x180 kernel/sched/core.c:6637
 percpu_rwsem_wait+0x2bd/0x300 kernel/locking/percpu-rwsem.c:162
 __percpu_down_read+0xda/0x120 kernel/locking/percpu-rwsem.c:177
 percpu_down_read include/linux/percpu-rwsem.h:65 [inline]
 cgroup_threadgroup_change_begin include/linux/cgroup-defs.h:748 [inline]
 exit_signals+0x3c0/0x4f0 kernel/signal.c:2963
 do_exit+0x578/0x2400 kernel/exit.c:827
 do_group_exit+0x217/0x2d0 kernel/exit.c:1022
 get_signal+0x1272/0x1350 kernel/signal.c:2871
 arch_do_signal_or_restart+0xb7/0x1240 arch/x86/kernel/signal.c:871
 exit_to_user_mode_loop+0x70/0x110 kernel/entry/common.c:174
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:210
 __syscall_exit_to_user_mode_work kernel/entry/common.c:292 [inline]
 syscall_exit_to_user_mode+0x16/0x40 kernel/entry/common.c:303
 do_syscall_64+0x58/0xa0 arch/x86/entry/common.c:87
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f778958f749
RSP: 002b:00007f778a3d20e8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00007f77897e5fa8 RCX: 00007f778958f749
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00007f77897e5fa8
RBP: 00007f77897e5fa0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f77897e6038 R14: 00007ffeb35239a0 R15: 00007ffeb3523a88
 </TASK>

Showing all locks held in the system:
1 lock held by rcu_tasks_kthre/12:
 #0: ffffffff8c92bab0 (rcu_tasks.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
1 lock held by rcu_tasks_trace/13:
 #0: ffffffff8c92c2d0 (rcu_tasks_trace.tasks_gp_mutex){+.+.}-{3:3}, at: rcu_tasks_one_gp+0x33/0xf00 kernel/rcu/tasks.h:517
1 lock held by khungtaskd/28:
 #0: ffffffff8c92b120 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:350 [inline]
 #0: ffffffff8c92b120 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:791 [inline]
 #0: ffffffff8c92b120 (rcu_read_lock){....}-{1:2}, at: debug_show_all_locks+0x51/0x290 kernel/locking/lockdep.c:6513
3 locks held by kworker/u4:3/46:
1 lock held by dhcpcd/3932:
 #0: ffffffff8c953d50 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: copy_process+0x248b/0x4020 kernel/fork.c:2446
2 locks held by getty/4027:
 #0: ffff88802fe01098 (&tty->ldisc_sem){++++}-{0:0}, at: tty_ldisc_ref_wait+0x21/0x70 drivers/tty/tty_ldisc.c:244
 #1: ffffc9000327b2f0 (&ldata->atomic_read_lock){+.+.}-{3:3}, at: n_tty_read+0x41b/0x1380 drivers/tty/n_tty.c:2198
1 lock held by udevd/4307:
 #0: ffffffff8c953d50 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x578/0x2400 kernel/exit.c:827
1 lock held by udevd/4377:
 #0: ffffffff8c953d50 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x578/0x2400 kernel/exit.c:827
5 locks held by kworker/u4:5/4385:
1 lock held by syz-executor/4393:
 #0: ffffffff8c953d50 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x578/0x2400 kernel/exit.c:827
3 locks held by syz-executor/4400:
 #0: ffff88801ff3e460 (sb_writers#10){.+.+}-{0:0}, at: vfs_write+0x256/0x960 fs/read_write.c:580
 #1: ffff888072db1888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e3/0x520 fs/kernfs/file.c:343
 #2: ffffffff8c953b68 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_lock include/linux/cgroup.h:442 [inline]
 #2: ffffffff8c953b68 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_kn_lock_live+0xee/0x230 kernel/cgroup/cgroup.c:1700
7 locks held by syz-executor/4405:
 #0: ffff88801e74e460 (sb_writers#11){.+.+}-{0:0}, at: vfs_write+0x256/0x960 fs/read_write.c:580
 #1: ffff888076bc5088 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e3/0x520 fs/kernfs/file.c:343
 #2: ffffffff8c953b68 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_lock include/linux/cgroup.h:442 [inline]
 #2: ffffffff8c953b68 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_kn_lock_live+0xee/0x230 kernel/cgroup/cgroup.c:1700
 #3: ffffffff8c7c7ab0 (cpu_hotplug_lock){++++}-{0:0}, at: cgroup_attach_lock kernel/cgroup/cgroup.c:2476 [inline]
 #3: ffffffff8c7c7ab0 (cpu_hotplug_lock){++++}-{0:0}, at: cgroup_procs_write_start+0x183/0x600 kernel/cgroup/cgroup.c:2982
 #4: ffffffff8c953d50 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: cgroup_attach_lock kernel/cgroup/cgroup.c:2478 [inline]
 #4: ffffffff8c953d50 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: cgroup_procs_write_start+0x199/0x600 kernel/cgroup/cgroup.c:2982
 #5: ffffffff8c9621e8 (cpuset_mutex){+.+.}-{3:3}, at: cpuset_attach+0xac/0x540 kernel/cgroup/cpuset.c:2647
 #6: ffff888077066a58 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock include/linux/mmap_lock.h:71 [inline]
 #6: ffff888077066a58 (&mm->mmap_lock){++++}-{3:3}, at: mpol_rebind_mm+0xbe/0x370 mm/mempolicy.c:386
3 locks held by syz-executor/4406:
 #0: ffff88801ff3e460 (sb_writers#10){.+.+}-{0:0}, at: vfs_write+0x256/0x960 fs/read_write.c:580
 #1: ffff88801dfa7888 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x1e3/0x520 fs/kernfs/file.c:343
 #2: ffffffff8c953b68 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_lock include/linux/cgroup.h:442 [inline]
 #2: ffffffff8c953b68 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_kn_lock_live+0xee/0x230 kernel/cgroup/cgroup.c:1700
1 lock held by syz.1.121/4725:
 #0: ffff8880304344d8 (&mm->mmap_lock){++++}-{3:3}, at: mmap_write_lock include/linux/mmap_lock.h:71 [inline]
 #0: ffff8880304344d8 (&mm->mmap_lock){++++}-{3:3}, at: exit_mmap+0x20f/0x8e0 mm/mmap.c:3258
1 lock held by syz.0.132/4745:
 #0: ffffffff8c953d50 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x578/0x2400 kernel/exit.c:827
1 lock held by syz.0.132/4746:
 #0: ffffffff8c953d50 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: do_exit+0x578/0x2400 kernel/exit.c:827

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

NMI backtrace for cpu 0
CPU: 0 PID: 28 Comm: khungtaskd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x168/0x22e lib/dump_stack.c:106
 nmi_cpu_backtrace+0x3f4/0x470 lib/nmi_backtrace.c:111
 nmi_trigger_cpumask_backtrace+0x1d4/0x450 lib/nmi_backtrace.c:62
 trigger_all_cpu_backtrace include/linux/nmi.h:148 [inline]
 check_hung_uninterruptible_tasks kernel/hung_task.c:220 [inline]
 watchdog+0xeee/0xf30 kernel/hung_task.c:377
 kthread+0x29d/0x330 kernel/kthread.c:376
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1
CPU: 1 PID: 3618 Comm: syslogd Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
RIP: 0010:begin_current_label_crit_section security/apparmor/include/cred.h:166 [inline]
RIP: 0010:aa_sk_perm+0x19e/0x920 security/apparmor/net.c:174
Code: c0 49 8d 5d 40 48 89 d8 48 c1 e8 03 42 80 3c 38 00 74 08 48 89 df e8 11 53 04 fe 48 8b 1b 48 89 de 48 81 e6 00 08 00 00 31 ff <e8> 8d 25 b4 fd 48 81 e3 00 08 00 00 75 0a e8 9f 21 b4 fd e9 e4 03
RSP: 0018:ffffc90003267aa0 EFLAGS: 00000246
RAX: 1ffff11002ec2b5e RBX: 000000000000029a RCX: 73e02d090127a500
RDX: ffff88807c97bb80 RSI: 0000000000000000 RDI: 0000000000000000
RBP: ffffc90003267b70 R08: dffffc0000000000 R09: ffffc90003267c58
R10: fffff5200064cf8d R11: 1ffff9200064cf8b R12: ffff88807c97c420
R13: ffff888017615ab0 R14: ffff88807e199fa8 R15: dffffc0000000000
FS:  00007feaf4ea0c80(0000) GS:ffff8880b8f00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f774a855000 CR3: 000000007ce76000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 security_socket_recvmsg+0x75/0xb0 security/security.c:2281
 sock_recvmsg net/socket.c:1038 [inline]
 sock_read_iter+0x240/0x370 net/socket.c:1121
 call_read_iter include/linux/fs.h:2259 [inline]
 new_sync_read fs/read_write.c:389 [inline]
 vfs_read+0x434/0x920 fs/read_write.c:470
 ksys_read+0x143/0x240 fs/read_write.c:613
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7feaf4ff0407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffd9fef92e0 EFLAGS: 00000202 ORIG_RAX: 0000000000000000
RAX: ffffffffffffffda RBX: 00007feaf4ea0c80 RCX: 00007feaf4ff0407
RDX: 00000000000000ff RSI: 000055576cbb5950 RDI: 0000000000000000
RBP: 000055576cbb5910 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 000055576cbb5999
R13: 0000000000000000 R14: 000055576cbb5950 R15: 0000555761a6bd98
 </TASK>

Crashes (12):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/01/10 14:50 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: task hung in cgroup_can_fork
2025/11/23 15:39 linux-6.1.y f6e38ae624cf 4fb8ef37 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: task hung in cgroup_can_fork
2025/10/09 01:39 linux-6.1.y 882efbdd9d34 7e2882b3 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: task hung in cgroup_can_fork
2025/10/04 18:09 linux-6.1.y 882efbdd9d34 49379ee0 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: task hung in cgroup_can_fork
2025/10/04 01:39 linux-6.1.y 882efbdd9d34 49379ee0 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: task hung in cgroup_can_fork
2025/10/03 14:58 linux-6.1.y 882efbdd9d34 49379ee0 .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: task hung in cgroup_can_fork
2025/10/01 09:40 linux-6.1.y 7b34dc04e4ff 65a0eece .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: task hung in cgroup_can_fork
2025/09/23 15:44 linux-6.1.y 363a599da6d9 0ac7291c .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: task hung in cgroup_can_fork
2026/01/10 03:10 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: task hung in cgroup_can_fork
2026/01/04 13:42 linux-6.1.y 50cbba13faa2 d6526ea3 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: task hung in cgroup_can_fork
2025/10/31 09:26 linux-6.1.y f6e38ae624cf 2c50b6a9 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: task hung in cgroup_can_fork
2025/09/24 22:34 linux-6.1.y 363a599da6d9 0abd0691 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-perf INFO: task hung in cgroup_can_fork
* Struck through repros no longer work on HEAD.