Re: [syzbot] [ppp?] inconsistent lock state in valid_state (4)

On Thu, Aug 22, 2024 at 1:00 AM syzbot
<[email protected]> wrote:
>
> syzbot has found a reproducer for the following issue on:
>
> HEAD commit:    b311c1b497e5 Merge tag '6.11-rc4-server-fixes' of git://gi..
> git tree:       upstream
> console output: https://syzkaller.appspot.com/x/log.txt?x=12dccc7b980000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=df2f0ed7e30a639d
> dashboard link: https://syzkaller.appspot.com/bug?extid=d43eb079c2addf2439c3
> compiler:       Debian clang version 15.0.6, GNU ld (GNU Binutils for Debian) 2.40
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=17cf93d5980000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=101bb693980000
>
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7bc7510fe41f/non_bootable_disk-b311c1b4.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/1c99fa48192f/vmlinux-b311c1b4.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/16d5710a012a/bzImage-b311c1b4.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: [email protected]
>
> ================================
> WARNING: inconsistent lock state
> 6.11.0-rc4-syzkaller-00019-gb311c1b497e5 #0 Not tainted
> --------------------------------
> inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
> ksoftirqd/0/16 [HC0[0]:SC1[1]:HE1:SE0] takes:
> ffff888039c531e0 (&pch->downl){+.?.}-{2:2}, at: spin_lock include/linux/spinlock.h:351 [inline]
> ffff888039c531e0 (&pch->downl){+.?.}-{2:2}, at: ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2272 [inline]
> ffff888039c531e0 (&pch->downl){+.?.}-{2:2}, at: ppp_input+0x18b/0xa10 drivers/net/ppp/ppp_generic.c:2304
> {SOFTIRQ-ON-W} state was registered at:
>   lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
>   __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+0x18b/0xa10 drivers/net/ppp/ppp_generic.c:2304
>   pppoe_rcv_core+0x117/0x310 drivers/net/ppp/pppoe.c:379
>   sk_backlog_rcv include/net/sock.h:1111 [inline]
>   __release_sock+0x243/0x350 net/core/sock.c:3004
>   release_sock+0x61/0x1f0 net/core/sock.c:3558
>   pppoe_sendmsg+0xd5/0x750 drivers/net/ppp/pppoe.c:903
>   sock_sendmsg_nosec net/socket.c:730 [inline]
>   __sock_sendmsg+0x221/0x270 net/socket.c:745
>   ____sys_sendmsg+0x525/0x7d0 net/socket.c:2597
>   ___sys_sendmsg net/socket.c:2651 [inline]
>   __sys_sendmmsg+0x3b2/0x740 net/socket.c:2737
>   __do_sys_sendmmsg net/socket.c:2766 [inline]
>   __se_sys_sendmmsg net/socket.c:2763 [inline]
>   __x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2763
>   do_syscall_x64 arch/x86/entry/common.c:52 [inline]
>   do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
>   entry_SYSCALL_64_after_hwframe+0x77/0x7f
> irq event stamp: 1309336
> hardirqs last  enabled at (1309336): [<ffffffff8bc0d5ff>] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline]
> hardirqs last  enabled at (1309336): [<ffffffff8bc0d5ff>] _raw_spin_unlock_irqrestore+0x8f/0x140 kernel/locking/spinlock.c:194
> hardirqs last disabled at (1309335): [<ffffffff8bc0d300>] __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:108 [inline]
> hardirqs last disabled at (1309335): [<ffffffff8bc0d300>] _raw_spin_lock_irqsave+0xb0/0x120 kernel/locking/spinlock.c:162
> softirqs last  enabled at (1309326): [<ffffffff81578ffa>] run_ksoftirqd+0xca/0x130 kernel/softirq.c:928
> softirqs last disabled at (1309331): [<ffffffff81578ffa>] run_ksoftirqd+0xca/0x130 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/0/16:
>  #0: ffffffff8e938320 (rcu_read_lock){....}-{1:2}, at: rcu_lock_acquire include/linux/rcupdate.h:326 [inline]
>  #0: ffffffff8e938320 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock include/linux/rcupdate.h:838 [inline]
>  #0: ffffffff8e938320 (rcu_read_lock){....}-{1:2}, at: ppp_channel_bridge_input drivers/net/ppp/ppp_generic.c:2267 [inline]
>  #0: ffffffff8e938320 (rcu_read_lock){....}-{1:2}, at: ppp_input+0x55/0xa10 drivers/net/ppp/ppp_generic.c:2304
>
> stack backtrace:
> CPU: 0 UID: 0 PID: 16 Comm: ksoftirqd/0 Not tainted 6.11.0-rc4-syzkaller-00019-gb311c1b497e5 #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:93 [inline]
>  dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119
>  valid_state+0x13a/0x1c0 kernel/locking/lockdep.c:4012
>  mark_lock_irq+0xbb/0xc20 kernel/locking/lockdep.c:4215
>  mark_lock+0x223/0x350 kernel/locking/lockdep.c:4677
>  __lock_acquire+0xbf9/0x2040 kernel/locking/lockdep.c:5096
>  lock_acquire+0x1ed/0x550 kernel/locking/lockdep.c:5759
>  __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+0x18b/0xa10 drivers/net/ppp/ppp_generic.c:2304
>  ppp_sync_process+0x71/0x160 drivers/net/ppp/ppp_synctty.c:490
>  tasklet_action_common+0x321/0x4d0 kernel/softirq.c:785
>  handle_softirqs+0x2c4/0x970 kernel/softirq.c:554
>  run_ksoftirqd+0xca/0x130 kernel/softirq.c:928
>  smpboot_thread_fn+0x544/0xa30 kernel/smpboot.c:164
>  kthread+0x2f0/0x390 kernel/kthread.c:389
>  ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
>  ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244
>  </TASK>
>
>
> ---
> If you want syzbot to run the reproducer, reply with:
> #syz test: git://repo/address.git branch-or-commit-hash
> If you attach or paste a git patch, syzbot will apply it before testing.

Bug probably added in

commit 4cf476ced45d7f12df30a68e833b263e7a2202d1
Author: Tom Parkin <[email protected]>
Date:   Thu Dec 10 15:50:57 2020 +0000

    ppp: add PPPIOCBRIDGECHAN and PPPIOCUNBRIDGECHAN ioctls



sk_backlog_rcv() is called without BH being blocked.

Fx would be :

diff --git a/drivers/net/ppp/ppp_generic.c b/drivers/net/ppp/ppp_generic.c
index eb9acfcaeb097496b5e28c87af13f5b4091a9bed..9d2656afba660a1a0eda5a53903b0f668a11abc9
100644
--- a/drivers/net/ppp/ppp_generic.c
+++ b/drivers/net/ppp/ppp_generic.c
@@ -2269,7 +2269,7 @@ static bool ppp_channel_bridge_input(struct
channel *pch, struct sk_buff *skb)
        if (!pchb)
                goto out_rcu;

-       spin_lock(&pchb->downl);
+       spin_lock_bh(&pchb->downl);
        if (!pchb->chan) {
                /* channel got unregistered */
                kfree_skb(skb);
@@ -2281,7 +2281,7 @@ static bool ppp_channel_bridge_input(struct
channel *pch, struct sk_buff *skb)
                kfree_skb(skb);

 outl:
-       spin_unlock(&pchb->downl);
+       spin_unlock_bh(&pchb->downl);
 out_rcu:
        rcu_read_unlock();