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Message-Id: <20240822110942.990-1-hdanton@sina.com>
Date: Thu, 22 Aug 2024 19:09:42 +0800
From: Hillf Danton <hdanton@...a.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: syzbot <syzbot+d43eb079c2addf2439c3@...kaller.appspotmail.com>,
Thomas Gleixner <tglx@...utronix.de>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Boqun Feng <boqun.feng@...il.com>,
linux-kernel@...r.kernel.org,
netdev@...r.kernel.org,
syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [ppp?] inconsistent lock state in valid_state (4)
On Thu, 22 Aug 2024 08:29:35 +0200 Eric Dumazet <edumazet@...gle.com>
> On Thu, Aug 22, 2024 at 1:00=E2=80=AFAM syzbot
> <syzbot+d43eb079c2addf2439c3@...kaller.appspotmail.com> wrote:
> >
> > syzbot has found a reproducer for the following issue on:
> >
> > HEAD commit: b311c1b497e5 Merge tag '6.11-rc4-server-fixes' of git://g=
> i..
> > git tree: upstream
> > console output: https://syzkaller.appspot.com/x/log.txt?x=3D12dccc7b98000=
> 0
> > kernel config: https://syzkaller.appspot.com/x/.config?x=3Ddf2f0ed7e30a6=
> 39d
> > dashboard link: https://syzkaller.appspot.com/bug?extid=3Dd43eb079c2addf2=
> 439c3
> > compiler: Debian clang version 15.0.6, GNU ld (GNU Binutils for Deb=
> ian) 2.40
> > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=3D17cf93d5980=
> 000
> > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=3D101bb69398000=
> 0
> >
> > Downloadable assets:
> > disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/7=
> bc7510fe41f/non_bootable_disk-b311c1b4.raw.xz
> > vmlinux: https://storage.googleapis.com/syzbot-assets/1c99fa48192f/vmlinu=
> x-b311c1b4.xz
> > kernel image: https://storage.googleapis.com/syzbot-assets/16d5710a012a/b=
> zImage-b311c1b4.xz
> >
> > IMPORTANT: if you fix the issue, please add the following tag to the comm=
> it:
> > Reported-by: syzbot+d43eb079c2addf2439c3@...kaller.appspotmail.com
> >
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
> =3D=3D=3D=3D=3D=3D=3D=3D
> > 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/s=
> pinlock.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 dri=
> vers/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_unlo=
> ck_irqrestore include/linux/spinlock_api_smp.h:151 [inline]
> > hardirqs last enabled at (1309336): [<ffffffff8bc0d5ff>] _raw_spin_unloc=
> k_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+0=
> xca/0x130 kernel/softirq.c:928
> > softirqs last disabled at (1309331): [<ffffffff81578ffa>] run_ksoftirqd+0=
> xca/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 i=
> nclude/linux/rcupdate.h:326 [inline]
> > #0: ffffffff8e938320 (rcu_read_lock){....}-{1:2}, at: rcu_read_lock incl=
> ude/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+0x55/0xa=
> 10 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
This report looks bogus to me given that kthread is unable to preempt a
userspace task with spinlock held.
> > 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 <tparkin@...alix.com>
> 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..9d2656afba660a1a0eda5a53903=
> b0f668a11abc9
> 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();
>
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