[syzbot] [cgroups?] possible deadlock in ptrace_attach

From: syzbot
Date: Thu Nov 16 2023 - 06:09:36 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=12e9b938e80000
kernel config: https://syzkaller.appspot.com/x/.config?x=f59345f1d0a928c
dashboard link: https://syzkaller.appspot.com/bug?extid=6b6c93afd6dd93d21e3e
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+6b6c93afd6dd93d21e3e@xxxxxxxxxxxxxxxxxxxxxxxxx

========================================================
WARNING: possible irq lock inversion dependency detected
6.7.0-rc1-next-20231116-syzkaller #0 Not tainted
--------------------------------------------------------
syz-executor.0/8349 just changed the state of lock:
ffff888026a040d8 (&sighand->siglock){+.+.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffff888026a040d8 (&sighand->siglock){+.+.}-{2:2}, at: class_spinlock_constructor include/linux/spinlock.h:530 [inline]
ffff888026a040d8 (&sighand->siglock){+.+.}-{2:2}, at: ptrace_set_stopped kernel/ptrace.c:391 [inline]
ffff888026a040d8 (&sighand->siglock){+.+.}-{2:2}, at: ptrace_attach+0x401/0x650 kernel/ptrace.c:478
but this lock was taken by another, SOFTIRQ-safe lock in the past:
(css_set_lock){..-.}-{2:2}

and interrupts could create inverse lock ordering between them.

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 ***

2 locks held by syz-executor.0/8349:
#0: ffff88801dc5c208 (&sig->cred_guard_mutex){+.+.}-{3:3}, at: class_mutex_intr_constructor include/linux/mutex.h:225 [inline]
#0: ffff88801dc5c208 (&sig->cred_guard_mutex){+.+.}-{3:3}, at: ptrace_attach+0x1eb/0x650 kernel/ptrace.c:455
#1: ffffffff8cc0a098 (tasklist_lock){++++}-{2:2}, at: class_write_lock_constructor include/linux/spinlock.h:564 [inline]
#1: ffffffff8cc0a098 (tasklist_lock){++++}-{2:2}, at: ptrace_attach+0x2c3/0x650 kernel/ptrace.c:464

the shortest dependencies between 2nd lock and 1st 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
rcu_lock_acquire include/linux/rcupdate.h:301 [inline]
rcu_read_lock include/linux/rcupdate.h:747 [inline]
__mod_lruvec_page_state+0xbf/0x390 mm/memcontrol.c:881
__lruvec_stat_mod_folio include/linux/vmstat.h:615 [inline]
folio_add_new_anon_rmap+0x19f/0xa00 mm/rmap.c:1331
wp_page_copy mm/memory.c:3193 [inline]
do_wp_page+0x1973/0x36d0 mm/memory.c:3515
handle_pte_fault mm/memory.c:5059 [inline]
__handle_mm_fault+0x1d7d/0x3d70 mm/memory.c:5184
handle_mm_fault+0x476/0xa00 mm/memory.c:5349
do_user_addr_fault+0x309/0x1000 arch/x86/mm/fault.c:1364
handle_page_fault arch/x86/mm/fault.c:1505 [inline]
exc_page_fault+0x5c/0xc0 arch/x86/mm/fault.c:1561
asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570
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
... acquired at:
__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_attach_task+0x5a8/0x8e0 kernel/cgroup/cgroup.c:2888
__cgroup_procs_write+0x311/0x540 kernel/cgroup/cgroup.c:5196
cgroup_procs_write+0x26/0x50 kernel/cgroup/cgroup.c:5209
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

-> (&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:
mark_usage kernel/locking/lockdep.c:4590 [inline]
__lock_acquire+0x967/0x3b10 kernel/locking/lockdep.c:5090
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

stack backtrace:
CPU: 0 PID: 8349 Comm: syz-executor.0 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_irq_inversion_bug.part.0+0x3e1/0x590 kernel/locking/lockdep.c:4079
print_irq_inversion_bug kernel/locking/lockdep.c:4032 [inline]
check_usage_forwards kernel/locking/lockdep.c:4110 [inline]
mark_lock_irq kernel/locking/lockdep.c:4242 [inline]
mark_lock+0x570/0xc50 kernel/locking/lockdep.c:4677
mark_usage kernel/locking/lockdep.c:4590 [inline]
__lock_acquire+0x967/0x3b10 kernel/locking/lockdep.c:5090
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
RIP: 0033:0x7f1cbae7cae9
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:00007f1cbbc160c8 EFLAGS: 00000246 ORIG_RAX: 0000000000000065
RAX: ffffffffffffffda RBX: 00007f1cbaf9c120 RCX: 00007f1cbae7cae9
RDX: 0000000000000000 RSI: 0000000000000198 RDI: 0000000000000010
RBP: 00007f1cbaec847a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007f1cbaf9c120 R15: 00007ffcf4911798
</TASK>

---
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