Re: [syzbot] [kernel?] inconsistent lock state in ptrace_attach

[syzbot]

syzbot has found a reproducer for 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=168778a8e80000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f59345f1d0a928c
dashboard link: https://syzkaller.appspot.com/bug?extid=cbb25bb9b4d29a773985
compiler:       gcc (Debian 12.2.0-14) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12e34b97680000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15c8aca7680000

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+cbb25bb9b4d29a773985@xxxxxxxxxxxxxxxxxxxxxxxxx

================================
WARNING: inconsistent lock state
6.7.0-rc1-next-20231116-syzkaller #0 Not tainted
--------------------------------
inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
syz-executor207/5059 [HC0[0]:SC0[0]:HE1:SE1] takes:
ffff888025c41298 (&sighand->siglock){?...}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffff888025c41298 (&sighand->siglock){?...}-{2:2}, at: class_spinlock_constructor include/linux/spinlock.h:530 [inline]
ffff888025c41298 (&sighand->siglock){?...}-{2:2}, at: ptrace_set_stopped kernel/ptrace.c:391 [inline]
ffff888025c41298 (&sighand->siglock){?...}-{2:2}, at: ptrace_attach+0x401/0x650 kernel/ptrace.c:478
{IN-HARDIRQ-W} state was registered 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]
  send_sigqueue+0x1d4/0x840 kernel/signal.c:1996
  posix_timer_event kernel/time/posix-timers.c:298 [inline]
  posix_timer_fn+0x181/0x3d0 kernel/time/posix-timers.c:324
  __run_hrtimer kernel/time/hrtimer.c:1688 [inline]
  __hrtimer_run_queues+0x20c/0xc20 kernel/time/hrtimer.c:1752
  hrtimer_interrupt+0x31b/0x800 kernel/time/hrtimer.c:1814
  local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1065 [inline]
  __sysvec_apic_timer_interrupt+0x10c/0x410 arch/x86/kernel/apic/apic.c:1082
  sysvec_apic_timer_interrupt+0x90/0xb0 arch/x86/kernel/apic/apic.c:1076
  asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:645
  __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline]
  _raw_spin_unlock_irqrestore+0x31/0x70 kernel/locking/spinlock.c:194
  spin_unlock_irqrestore include/linux/spinlock.h:406 [inline]
  unlock_timer kernel/time/posix-timers.c:128 [inline]
  do_timer_settime+0x260/0x2f0 kernel/time/posix-timers.c:934
  __do_sys_timer_settime kernel/time/posix-timers.c:954 [inline]
  __se_sys_timer_settime kernel/time/posix-timers.c:940 [inline]
  __x64_sys_timer_settime+0x266/0x2c0 kernel/time/posix-timers.c:940
  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
irq event stamp: 13807
hardirqs last  enabled at (13807): [<ffffffff8a84a34e>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline]
hardirqs last  enabled at (13807): [<ffffffff8a84a34e>] _raw_spin_unlock_irqrestore+0x4e/0x70 kernel/locking/spinlock.c:194
hardirqs last disabled at (13806): [<ffffffff8a84a0fe>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:108 [inline]
hardirqs last disabled at (13806): [<ffffffff8a84a0fe>] _raw_spin_lock_irqsave+0x4e/0x50 kernel/locking/spinlock.c:162
softirqs last  enabled at (13794): [<ffffffff813146a1>] local_bh_enable include/linux/bottom_half.h:33 [inline]
softirqs last  enabled at (13794): [<ffffffff813146a1>] fpregs_unlock arch/x86/include/asm/fpu/api.h:80 [inline]
softirqs last  enabled at (13794): [<ffffffff813146a1>] restore_fpregs_from_user arch/x86/kernel/fpu/signal.c:330 [inline]
softirqs last  enabled at (13794): [<ffffffff813146a1>] __fpu_restore_sig+0x6a1/0x13a0 arch/x86/kernel/fpu/signal.c:361
softirqs last disabled at (13792): [<ffffffff81314365>] local_bh_disable include/linux/bottom_half.h:20 [inline]
softirqs last disabled at (13792): [<ffffffff81314365>] fpregs_lock arch/x86/include/asm/fpu/api.h:72 [inline]
softirqs last disabled at (13792): [<ffffffff81314365>] restore_fpregs_from_user arch/x86/kernel/fpu/signal.c:284 [inline]
softirqs last disabled at (13792): [<ffffffff81314365>] __fpu_restore_sig+0x365/0x13a0 arch/x86/kernel/fpu/signal.c:361

other info that might help us debug this:
 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

2 locks held by syz-executor207/5059:
 #0: ffff88801d66e3c8 (&sig->cred_guard_mutex){+.+.}-{3:3}, at: class_mutex_intr_constructor include/linux/mutex.h:225 [inline]
 #0: ffff88801d66e3c8 (&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

stack backtrace:
CPU: 0 PID: 5059 Comm: syz-executor207 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_usage_bug kernel/locking/lockdep.c:3970 [inline]
 valid_state kernel/locking/lockdep.c:4012 [inline]
 mark_lock_irq kernel/locking/lockdep.c:4215 [inline]
 mark_lock+0x91a/0xc50 kernel/locking/lockdep.c:4677
 mark_usage kernel/locking/lockdep.c:4586 [inline]
 __lock_acquire+0x919/0x3b10 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: 0033:0x7f726faf87f9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 c1 17 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:00007f726fab7158 EFLAGS: 00000246 ORIG_RAX: 0000000000000065
RAX: ffffffffffffffda RBX: 00007f726fb7f328 RCX: 00007f726faf87f9
RDX: 0000000000000000 RSI: 00000000000013c4 RDI: 0000000000000010
RBP: 00007f726fb7f320 R08: 00007f726fab76c0 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00007f726fb7f32c
R13: 0000000000000000 R14: 00007ffd413eb1b0 R15: 00007ffd413eb298
 </TASK>


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