syzbot

================================
WARNING: inconsistent lock state
6.11.0-rc7-syzkaller-g5f5673607153 #0 Not tainted
--------------------------------
inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
ksoftirqd/1/24 [HC0[0]:SC1[1]:HE1:SE0] takes:
ffff0000db7f11e0 (&pch->downl){+.?.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
ffff0000db7f11e0 (&pch->downl){+.?.}-{2:2}, at: ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2272 [inline]
ffff0000db7f11e0 (&pch->downl){+.?.}-{2:2}, at: ppp_input+0x16c/0x854 drivers/net/ppp/ppp_generic.c:2304
{SOFTIRQ-ON-W} state was registered at:
  lock_acquire+0x240/0x728 kernel/locking/lockdep.c:5759
  __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
  _raw_spin_lock+0x48/0x60 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+0x16c/0x854 drivers/net/ppp/ppp_generic.c:2304
  pppoe_rcv_core+0xfc/0x314 drivers/net/ppp/pppoe.c:379
  sk_backlog_rcv include/net/sock.h:1111 [inline]
  __release_sock+0x1a8/0x3d8 net/core/sock.c:3004
  release_sock+0x68/0x1b8 net/core/sock.c:3558
  pppoe_sendmsg+0xc8/0x5d8 drivers/net/ppp/pppoe.c:903
  sock_sendmsg_nosec net/socket.c:730 [inline]
  __sock_sendmsg net/socket.c:745 [inline]
  __sys_sendto+0x374/0x4f4 net/socket.c:2204
  __do_sys_sendto net/socket.c:2216 [inline]
  __se_sys_sendto net/socket.c:2212 [inline]
  __arm64_sys_sendto+0xd8/0xf8 net/socket.c:2212
  __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline]
  invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49
  el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132
  do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151
  el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:712
  el0t_64_sync_handler+0x84/0xfc arch/arm64/kernel/entry-common.c:730
  el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598
irq event stamp: 282914
hardirqs last  enabled at (282914): [<ffff80008b42e30c>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline]
hardirqs last  enabled at (282914): [<ffff80008b42e30c>] _raw_spin_unlock_irqrestore+0x38/0x98 kernel/locking/spinlock.c:194
hardirqs last disabled at (282913): [<ffff80008b42e13c>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:108 [inline]
hardirqs last disabled at (282913): [<ffff80008b42e13c>] _raw_spin_lock_irqsave+0x2c/0x7c kernel/locking/spinlock.c:162
softirqs last  enabled at (282904): [<ffff8000801f8e88>] softirq_handle_end kernel/softirq.c:400 [inline]
softirqs last  enabled at (282904): [<ffff8000801f8e88>] handle_softirqs+0xa3c/0xbfc kernel/softirq.c:582
softirqs last disabled at (282909): [<ffff8000801fbdf8>] run_ksoftirqd+0x70/0x158 kernel/softirq.c:928

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/1/24:
 #0: ffff80008f74dfa0 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire+0x10/0x4c include/linux/rcupdate.h:325

stack backtrace:
CPU: 1 UID: 0 PID: 24 Comm: ksoftirqd/1 Not tainted 6.11.0-rc7-syzkaller-g5f5673607153 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
Call trace:
 dump_backtrace+0x1b8/0x1e4 arch/arm64/kernel/stacktrace.c:319
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:326
 __dump_stack lib/dump_stack.c:93 [inline]
 dump_stack_lvl+0xe4/0x150 lib/dump_stack.c:119
 dump_stack+0x1c/0x28 lib/dump_stack.c:128
 print_usage_bug+0x698/0x9ac kernel/locking/lockdep.c:4000
 mark_lock_irq+0x980/0xd2c
 mark_lock+0x258/0x360 kernel/locking/lockdep.c:4677
 __lock_acquire+0xf48/0x779c kernel/locking/lockdep.c:5096
 lock_acquire+0x240/0x728 kernel/locking/lockdep.c:5759
 __raw_spin_lock include/linux/spinlock_api_smp.h:133 [inline]
 _raw_spin_lock+0x48/0x60 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+0x16c/0x854 drivers/net/ppp/ppp_generic.c:2304
 ppp_async_process+0x98/0x150 drivers/net/ppp/ppp_async.c:495
 tasklet_action_common+0x318/0x3f4 kernel/softirq.c:785
 tasklet_action+0x68/0x8c kernel/softirq.c:811
 handle_softirqs+0x2e4/0xbfc kernel/softirq.c:554
 run_ksoftirqd+0x70/0x158 kernel/softirq.c:928
 smpboot_thread_fn+0x4b0/0x90c kernel/smpboot.c:164
 kthread+0x288/0x310 kernel/kthread.c:389
 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860