================================
WARNING: inconsistent lock state
6.11.0-syzkaller-12113-ge7ed34365879 #0 Not tainted
--------------------------------
inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
ksoftirqd/1/29 [HC0[0]:SC1[1]:HE1:SE0] takes:
ffff8880613341e0 (&pch->downl){+.?.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffff8880613341e0 (&pch->downl){+.?.}-{2:2}, at: ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2272 [inline]
ffff8880613341e0 (&pch->downl){+.?.}-{2:2}, at: ppp_input+0x104/0xbb0 drivers/net/ppp/ppp_generic.c:2304
{SOFTIRQ-ON-W} state was registered at:
  lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5825
  __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]
  ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2272 [inline]
  ppp_input+0x104/0xbb0 drivers/net/ppp/ppp_generic.c:2304
  pppoe_rcv_core+0x22c/0x320 drivers/net/ppp/pppoe.c:379
  sk_backlog_rcv include/net/sock.h:1113 [inline]
  __release_sock+0x35f/0x400 net/core/sock.c:3072
  release_sock+0x5a/0x220 net/core/sock.c:3626
  pppoe_sendmsg+0x625/0x7c0 drivers/net/ppp/pppoe.c:903
  sock_sendmsg_nosec net/socket.c:729 [inline]
  __sock_sendmsg net/socket.c:744 [inline]
  ____sys_sendmsg+0x9ae/0xb40 net/socket.c:2602
  ___sys_sendmsg+0x135/0x1e0 net/socket.c:2656
  __sys_sendmmsg+0x2a5/0x450 net/socket.c:2735
  __compat_sys_sendmmsg net/compat.c:360 [inline]
  __do_compat_sys_sendmmsg net/compat.c:367 [inline]
  __se_compat_sys_sendmmsg net/compat.c:364 [inline]
  __ia32_compat_sys_sendmmsg+0x9d/0x100 net/compat.c:364
  do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
  __do_fast_syscall_32+0x73/0x120 arch/x86/entry/common.c:386
  do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
  entry_SYSENTER_compat_after_hwframe+0x84/0x8e
irq event stamp: 687126
hardirqs last  enabled at (687126): [<ffffffff81502af4>] __local_bh_enable_ip+0xa4/0x120 kernel/softirq.c:387
hardirqs last disabled at (687125): [<ffffffff81502b1d>] __local_bh_enable_ip+0xcd/0x120 kernel/softirq.c:364
softirqs last  enabled at (687114): [<ffffffff8150259b>] softirq_handle_end kernel/softirq.c:400 [inline]
softirqs last  enabled at (687114): [<ffffffff8150259b>] handle_softirqs+0x5bb/0x8f0 kernel/softirq.c:582
softirqs last disabled at (687119): [<ffffffff8150291a>] run_ksoftirqd kernel/softirq.c:927 [inline]
softirqs last disabled at (687119): [<ffffffff8150291a>] run_ksoftirqd+0x3a/0x60 kernel/softirq.c:919

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

       CPU0
       ----
  lock(&pch->downl);
  <Interrupt>
    lock(&pch->downl);

 *** DEADLOCK ***

1 lock held by ksoftirqd/1/29:
 #0: ffffffff8ddb7800 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:337 [inline]
 #0: ffffffff8ddb7800 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:849 [inline]
 #0: ffffffff8ddb7800 (rcu_read_lock){....}-{1:2}, at: ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2267 [inline]
 #0: ffffffff8ddb7800 (rcu_read_lock){....}-{1:2}, at: ppp_input+0x70/0xbb0 drivers/net/ppp/ppp_generic.c:2304

stack backtrace:
CPU: 1 UID: 0 PID: 29 Comm: ksoftirqd/1 Not tainted 6.11.0-syzkaller-12113-ge7ed34365879 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
 print_usage_bug.part.0+0x3a2/0x560 kernel/locking/lockdep.c:4038
 print_usage_bug kernel/locking/lockdep.c:4006 [inline]
 valid_state kernel/locking/lockdep.c:4052 [inline]
 mark_lock_irq kernel/locking/lockdep.c:4263 [inline]
 mark_lock+0x92d/0xc60 kernel/locking/lockdep.c:4725
 mark_usage kernel/locking/lockdep.c:4614 [inline]
 __lock_acquire+0x11e1/0x3ce0 kernel/locking/lockdep.c:5156
 lock_acquire.part.0+0x11b/0x380 kernel/locking/lockdep.c:5825
 __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]
 ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2272 [inline]
 ppp_input+0x104/0xbb0 drivers/net/ppp/ppp_generic.c:2304
 ppp_async_process+0x37/0x150 drivers/net/ppp/ppp_async.c:495
 tasklet_action_common+0x24c/0x3e0 kernel/softirq.c:784
 handle_softirqs+0x213/0x8f0 kernel/softirq.c:554
 run_ksoftirqd kernel/softirq.c:927 [inline]
 run_ksoftirqd+0x3a/0x60 kernel/softirq.c:919
 smpboot_thread_fn+0x661/0xa30 kernel/smpboot.c:164
 kthread+0x2c1/0x3a0 kernel/kthread.c:389
 ret_from_fork+0x45/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
 </TASK>