On Thu, Aug 22, 2024 at 1:00 AM syzbot <syzbot+d43eb079c2addf2439c3@xxxxxxxxxxxxxxxxxxxxxxxxx> 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: syzbot+d43eb079c2addf2439c3@xxxxxxxxxxxxxxxxxxxxxxxxx > > ================================ > 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 <tparkin@xxxxxxxxxxx> 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();
