[syzbot] [cgroups?] possible deadlock in cgroup_free

From: syzbot
Date: Thu Nov 16 2023 - 06:08:31 EST

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Hello,

syzbot found the following issue on:

HEAD commit: f31817cbcf48 Add linux-next specific files for 20231116
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=17d0aca7680000
kernel config: https://syzkaller.appspot.com/x/.config?x=f59345f1d0a928c
dashboard link: https://syzkaller.appspot.com/bug?extid=cef555184e66963dabc2
compiler: gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/987488cb251e/disk-f31817cb.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/6d4a82d8bd4b/vmlinux-f31817cb.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fc43dee9cb86/bzImage-f31817cb.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+cef555184e66963dabc2@xxxxxxxxxxxxxxxxxxxxxxxxx

=====================================================
WARNING: SOFTIRQ-safe -> SOFTIRQ-unsafe lock order detected
6.7.0-rc1-next-20231116-syzkaller #0 Not tainted
-----------------------------------------------------
syz-executor.3/8188 [HC0[0]:SC0[0]:HE0:SE1] is trying to acquire:
ffff88801f641298 (&sighand->siglock){+.+.}-{2:2}, at: __lock_task_sighand+0xc2/0x340 kernel/signal.c:1422

and this task is already holding:
ffffffff8cff86b8 (css_set_lock){..-.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:376 [inline]
ffffffff8cff86b8 (css_set_lock){..-.}-{2:2}, at: cgroup_migrate_execute+0xd8/0x1230 kernel/cgroup/cgroup.c:2566
which would create a new lock dependency:
(css_set_lock){..-.}-{2:2} -> (&sighand->siglock){+.+.}-{2:2}

but this new dependency connects a SOFTIRQ-irq-safe lock:
(css_set_lock){..-.}-{2:2}

... which became SOFTIRQ-irq-safe at:
lock_acquire kernel/locking/lockdep.c:5753 [inline]
lock_acquire+0x1b1/0x530 kernel/locking/lockdep.c:5718
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x3a/0x50 kernel/locking/spinlock.c:162
put_css_set kernel/cgroup/cgroup-internal.h:208 [inline]
put_css_set kernel/cgroup/cgroup-internal.h:196 [inline]
cgroup_free+0x7c/0x1d0 kernel/cgroup/cgroup.c:6748
__put_task_struct+0x10b/0x3d0 kernel/fork.c:992
put_task_struct include/linux/sched/task.h:136 [inline]
put_task_struct include/linux/sched/task.h:123 [inline]
delayed_put_task_struct+0x22c/0x2d0 kernel/exit.c:227
rcu_do_batch kernel/rcu/tree.c:2158 [inline]
rcu_core+0x828/0x16b0 kernel/rcu/tree.c:2431
__do_softirq+0x216/0x8d5 kernel/softirq.c:553
invoke_softirq kernel/softirq.c:427 [inline]
__irq_exit_rcu kernel/softirq.c:632 [inline]
irq_exit_rcu+0xb5/0x120 kernel/softirq.c:644
sysvec_apic_timer_interrupt+0x95/0xb0 arch/x86/kernel/apic/apic.c:1076
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:645
lock_acquire+0x1f2/0x530 kernel/locking/lockdep.c:5721
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:351 [inline]
lockref_put_or_lock+0x18/0x80 lib/lockref.c:147
fast_dput fs/dcache.c:775 [inline]
fast_dput fs/dcache.c:765 [inline]
dput+0x4c4/0xd90 fs/dcache.c:900
shmem_unlink+0x1bc/0x310 mm/shmem.c:3373
shmem_rename2+0x1ff/0x3b0 mm/shmem.c:3451
vfs_rename+0xe20/0x1c30 fs/namei.c:4844
do_renameat2+0xc3c/0xdc0 fs/namei.c:4996
__do_sys_rename fs/namei.c:5042 [inline]
__se_sys_rename fs/namei.c:5040 [inline]
__x64_sys_rename+0x81/0xa0 fs/namei.c:5040
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x40/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x62/0x6a

to a SOFTIRQ-irq-unsafe lock:
(&sighand->siglock){+.+.}-{2:2}

... which became SOFTIRQ-irq-unsafe at:
...
lock_acquire kernel/locking/lockdep.c:5753 [inline]
lock_acquire+0x1b1/0x530 kernel/locking/lockdep.c:5718
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:351 [inline]
class_spinlock_constructor include/linux/spinlock.h:530 [inline]
ptrace_set_stopped kernel/ptrace.c:391 [inline]
ptrace_attach+0x401/0x650 kernel/ptrace.c:478
__do_sys_ptrace+0x204/0x230 kernel/ptrace.c:1290
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x40/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x62/0x6a

other info that might help us debug this:

Possible interrupt unsafe locking scenario:

CPU0 CPU1
---- ----
lock(&sighand->siglock);
local_irq_disable();
lock(css_set_lock);
lock(&sighand->siglock);
<Interrupt>
lock(css_set_lock);

*** DEADLOCK ***

8 locks held by syz-executor.3/8188:
#0: ffff88801d0e0d48 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0xe7/0x170 fs/file.c:1177
#1: ffff888014b44420 (sb_writers#10){.+.+}-{0:0}, at: ksys_write+0x12f/0x250 fs/read_write.c:637
#2: ffff88807ad7f088 (&of->mutex){+.+.}-{3:3}, at: kernfs_fop_write_iter+0x27d/0x500 fs/kernfs/file.c:325
#3: ffffffff8cff8768 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_lock include/linux/cgroup.h:368 [inline]
#3: ffffffff8cff8768 (cgroup_mutex){+.+.}-{3:3}, at: cgroup_lock_and_drain_offline+0xad/0x6d0 kernel/cgroup/cgroup.c:3092
#4: ffffffff8ce51f70 (cpu_hotplug_lock){++++}-{0:0}, at: cgroup_attach_lock kernel/cgroup/cgroup.c:2413 [inline]
#4: ffffffff8ce51f70 (cpu_hotplug_lock){++++}-{0:0}, at: cgroup_update_dfl_csses+0x2fb/0x640 kernel/cgroup/cgroup.c:3050
#5: ffffffff8cff8530 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: cgroup_attach_lock kernel/cgroup/cgroup.c:2415 [inline]
#5: ffffffff8cff8530 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: cgroup_attach_lock kernel/cgroup/cgroup.c:2411 [inline]
#5: ffffffff8cff8530 (cgroup_threadgroup_rwsem){++++}-{0:0}, at: cgroup_update_dfl_csses+0x3d1/0x640 kernel/cgroup/cgroup.c:3050
#6: ffffffff8cff86b8 (css_set_lock){..-.}-{2:2}, at: spin_lock_irq include/linux/spinlock.h:376 [inline]
#6: ffffffff8cff86b8 (css_set_lock){..-.}-{2:2}, at: cgroup_migrate_execute+0xd8/0x1230 kernel/cgroup/cgroup.c:2566
#7: ffffffff8cfad060 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:301 [inline]
#7: ffffffff8cfad060 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:747 [inline]
#7: ffffffff8cfad060 (rcu_read_lock){....}-{1:2}, at: __lock_task_sighand+0x3f/0x340 kernel/signal.c:1405

the dependencies between SOFTIRQ-irq-safe lock and the holding lock:
-> (css_set_lock){..-.}-{2:2} {
IN-SOFTIRQ-W at:
lock_acquire kernel/locking/lockdep.c:5753 [inline]
lock_acquire+0x1b1/0x530 kernel/locking/lockdep.c:5718
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x3a/0x50 kernel/locking/spinlock.c:162
put_css_set kernel/cgroup/cgroup-internal.h:208 [inline]
put_css_set kernel/cgroup/cgroup-internal.h:196 [inline]
cgroup_free+0x7c/0x1d0 kernel/cgroup/cgroup.c:6748
__put_task_struct+0x10b/0x3d0 kernel/fork.c:992
put_task_struct include/linux/sched/task.h:136 [inline]
put_task_struct include/linux/sched/task.h:123 [inline]
delayed_put_task_struct+0x22c/0x2d0 kernel/exit.c:227
rcu_do_batch kernel/rcu/tree.c:2158 [inline]
rcu_core+0x828/0x16b0 kernel/rcu/tree.c:2431
__do_softirq+0x216/0x8d5 kernel/softirq.c:553
invoke_softirq kernel/softirq.c:427 [inline]
__irq_exit_rcu kernel/softirq.c:632 [inline]
irq_exit_rcu+0xb5/0x120 kernel/softirq.c:644
sysvec_apic_timer_interrupt+0x95/0xb0 arch/x86/kernel/apic/apic.c:1076
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:645
lock_acquire+0x1f2/0x530 kernel/locking/lockdep.c:5721
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:351 [inline]
lockref_put_or_lock+0x18/0x80 lib/lockref.c:147
fast_dput fs/dcache.c:775 [inline]
fast_dput fs/dcache.c:765 [inline]
dput+0x4c4/0xd90 fs/dcache.c:900
shmem_unlink+0x1bc/0x310 mm/shmem.c:3373
shmem_rename2+0x1ff/0x3b0 mm/shmem.c:3451
vfs_rename+0xe20/0x1c30 fs/namei.c:4844
do_renameat2+0xc3c/0xdc0 fs/namei.c:4996
__do_sys_rename fs/namei.c:5042 [inline]
__se_sys_rename fs/namei.c:5040 [inline]
__x64_sys_rename+0x81/0xa0 fs/namei.c:5040
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x40/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x62/0x6a
INITIAL USE at:
lock_acquire kernel/locking/lockdep.c:5753 [inline]
lock_acquire+0x1b1/0x530 kernel/locking/lockdep.c:5718
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
_raw_spin_lock_irq+0x36/0x50 kernel/locking/spinlock.c:170
spin_lock_irq include/linux/spinlock.h:376 [inline]
cgroup_setup_root+0x62c/0xa00 kernel/cgroup/cgroup.c:2138
cgroup_init+0x23f/0x1100 kernel/cgroup/cgroup.c:6120
start_kernel+0x385/0x480 init/main.c:1063
x86_64_start_reservations+0x18/0x30 arch/x86/kernel/head64.c:555
x86_64_start_kernel+0xb2/0xc0 arch/x86/kernel/head64.c:536
secondary_startup_64_no_verify+0x166/0x16b
}
... key at: [<ffffffff8cff86b8>] css_set_lock+0x18/0x60

the dependencies between the lock to be acquired
and SOFTIRQ-irq-unsafe lock:
-> (&sighand->siglock){+.+.}-{2:2} {
HARDIRQ-ON-W at:
lock_acquire kernel/locking/lockdep.c:5753 [inline]
lock_acquire+0x1b1/0x530 kernel/locking/lockdep.c:5718
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:351 [inline]
class_spinlock_constructor include/linux/spinlock.h:530 [inline]
ptrace_set_stopped kernel/ptrace.c:391 [inline]
ptrace_attach+0x401/0x650 kernel/ptrace.c:478
__do_sys_ptrace+0x204/0x230 kernel/ptrace.c:1290
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x40/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x62/0x6a
SOFTIRQ-ON-W at:
lock_acquire kernel/locking/lockdep.c:5753 [inline]
lock_acquire+0x1b1/0x530 kernel/locking/lockdep.c:5718
__raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
_raw_spin_lock+0x2e/0x40 kernel/locking/spinlock.c:154
spin_lock include/linux/spinlock.h:351 [inline]
class_spinlock_constructor include/linux/spinlock.h:530 [inline]
ptrace_set_stopped kernel/ptrace.c:391 [inline]
ptrace_attach+0x401/0x650 kernel/ptrace.c:478
__do_sys_ptrace+0x204/0x230 kernel/ptrace.c:1290
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x40/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x62/0x6a
INITIAL USE at:
lock_acquire kernel/locking/lockdep.c:5753 [inline]
lock_acquire+0x1b1/0x530 kernel/locking/lockdep.c:5718
__raw_spin_lock_irq include/linux/spinlock_api_smp.h:119 [inline]
_raw_spin_lock_irq+0x36/0x50 kernel/locking/spinlock.c:170
spin_lock_irq include/linux/spinlock.h:376 [inline]
calculate_sigpending+0x44/0xa0 kernel/signal.c:197
ret_from_fork+0x23/0x80 arch/x86/kernel/process.c:143
ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:242
}
... key at: [<ffffffff90b49f80>] __key.341+0x0/0x40
... acquired at:
lock_acquire kernel/locking/lockdep.c:5753 [inline]
lock_acquire+0x1b1/0x530 kernel/locking/lockdep.c:5718
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x3a/0x50 kernel/locking/spinlock.c:162
__lock_task_sighand+0xc2/0x340 kernel/signal.c:1422
lock_task_sighand include/linux/sched/signal.h:748 [inline]
cgroup_freeze_task+0x80/0x190 kernel/cgroup/freezer.c:160
cgroup_freezer_migrate_task+0x1b7/0x3a0 kernel/cgroup/freezer.c:257
cgroup_migrate_execute+0x2d3/0x1230 kernel/cgroup/cgroup.c:2580
cgroup_update_dfl_csses+0x51b/0x640 kernel/cgroup/cgroup.c:3068
cgroup_apply_control kernel/cgroup/cgroup.c:3308 [inline]
cgroup_subtree_control_write+0xb94/0xed0 kernel/cgroup/cgroup.c:3453
cgroup_file_write+0x209/0x7c0 kernel/cgroup/cgroup.c:4092
kernfs_fop_write_iter+0x33f/0x500 fs/kernfs/file.c:334
call_write_iter include/linux/fs.h:2021 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x64d/0xdf0 fs/read_write.c:584
ksys_write+0x12f/0x250 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x40/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x62/0x6a

stack backtrace:
CPU: 1 PID: 8188 Comm: syz-executor.3 Not tainted 6.7.0-rc1-next-20231116-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/10/2023
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:88 [inline]
dump_stack_lvl+0xd9/0x1b0 lib/dump_stack.c:106
print_bad_irq_dependency kernel/locking/lockdep.c:2626 [inline]
check_irq_usage+0xe18/0x1470 kernel/locking/lockdep.c:2865
check_prev_add kernel/locking/lockdep.c:3138 [inline]
check_prevs_add kernel/locking/lockdep.c:3253 [inline]
validate_chain kernel/locking/lockdep.c:3868 [inline]
__lock_acquire+0x247c/0x3b10 kernel/locking/lockdep.c:5136
lock_acquire kernel/locking/lockdep.c:5753 [inline]
lock_acquire+0x1b1/0x530 kernel/locking/lockdep.c:5718
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
_raw_spin_lock_irqsave+0x3a/0x50 kernel/locking/spinlock.c:162
__lock_task_sighand+0xc2/0x340 kernel/signal.c:1422
lock_task_sighand include/linux/sched/signal.h:748 [inline]
cgroup_freeze_task+0x80/0x190 kernel/cgroup/freezer.c:160
cgroup_freezer_migrate_task+0x1b7/0x3a0 kernel/cgroup/freezer.c:257
cgroup_migrate_execute+0x2d3/0x1230 kernel/cgroup/cgroup.c:2580
cgroup_update_dfl_csses+0x51b/0x640 kernel/cgroup/cgroup.c:3068
cgroup_apply_control kernel/cgroup/cgroup.c:3308 [inline]
cgroup_subtree_control_write+0xb94/0xed0 kernel/cgroup/cgroup.c:3453
cgroup_file_write+0x209/0x7c0 kernel/cgroup/cgroup.c:4092
kernfs_fop_write_iter+0x33f/0x500 fs/kernfs/file.c:334
call_write_iter include/linux/fs.h:2021 [inline]
new_sync_write fs/read_write.c:491 [inline]
vfs_write+0x64d/0xdf0 fs/read_write.c:584
ksys_write+0x12f/0x250 fs/read_write.c:637
do_syscall_x64 arch/x86/entry/common.c:51 [inline]
do_syscall_64+0x40/0x110 arch/x86/entry/common.c:82
entry_SYSCALL_64_after_hwframe+0x62/0x6a
RIP: 0033:0x7f83f387cae9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f83f466d0c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f83f399bf80 RCX: 00007f83f387cae9
RDX: 0000000000000006 RSI: 0000000020000100 RDI: 0000000000000004
RBP: 00007f83f38c847a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000000b R14: 00007f83f399bf80 R15: 00007ffdda059fd8
</TASK>

---
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Next message: syzbot: "[syzbot] [kernel?] inconsistent lock state in __lock_task_sighand"
Previous message: Mark Tseng: "[PATCH v2 0/3] soc: mediatek: svs: add support for MT8186 and"
Next in thread: syzbot: "Re: [syzbot] [cgroups?] possible deadlock in cgroup_free"
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