Messages in this thread | | | From | Eric Dumazet <> | Date | Mon, 31 Jan 2022 12:51:20 -0800 | Subject | Re: [syzbot] possible deadlock in ___neigh_create |
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On Mon, Jan 31, 2022 at 12:48 PM syzbot <syzbot+5239d0e1778a500d477a@syzkaller.appspotmail.com> wrote: > > Hello, > > syzbot found the following issue on: > > HEAD commit: 6449520391df net: stmmac: properly handle with runtime pm .. > git tree: net > console output: https://syzkaller.appspot.com/x/log.txt?x=111187e0700000 > kernel config: https://syzkaller.appspot.com/x/.config?x=a6620d0aab7dd315 > dashboard link: https://syzkaller.appspot.com/bug?extid=5239d0e1778a500d477a > compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2 > > Unfortunately, I don't have any reproducer for this issue yet. > > IMPORTANT: if you fix the issue, please add the following tag to the commit: > Reported-by: syzbot+5239d0e1778a500d477a@syzkaller.appspotmail.com > > ============================================ > WARNING: possible recursive locking detected > 5.17.0-rc1-syzkaller-00210-g6449520391df #0 Not tainted > -------------------------------------------- > kworker/0:16/14617 is trying to acquire lock: > ffffffff8d4dd370 (&tbl->lock){++-.}-{2:2}, at: ___neigh_create+0x9e1/0x2990 net/core/neighbour.c:652 > > but task is already holding lock: > ffffffff8d4dd370 (&tbl->lock){++-.}-{2:2}, at: neigh_managed_work+0x35/0x250 net/core/neighbour.c:1572 > > other info that might help us debug this: > Possible unsafe locking scenario: > > CPU0 > ---- > lock(&tbl->lock); > lock(&tbl->lock); > > *** DEADLOCK *** > > May be due to missing lock nesting notation > > 5 locks held by kworker/0:16/14617: > #0: ffff888010c65d38 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline] > #0: ffff888010c65d38 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: arch_atomic_long_set include/linux/atomic/atomic-long.h:41 [inline] > #0: ffff888010c65d38 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: atomic_long_set include/linux/atomic/atomic-instrumented.h:1280 [inline] > #0: ffff888010c65d38 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: set_work_data kernel/workqueue.c:631 [inline] > #0: ffff888010c65d38 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: set_work_pool_and_clear_pending kernel/workqueue.c:658 [inline] > #0: ffff888010c65d38 ((wq_completion)events_power_efficient){+.+.}-{0:0}, at: process_one_work+0x890/0x1650 kernel/workqueue.c:2278 > #1: ffffc9000293fdb8 ((work_completion)(&(&tbl->managed_work)->work)){+.+.}-{0:0}, at: process_one_work+0x8c4/0x1650 kernel/workqueue.c:2282 > #2: ffffffff8d4dd370 (&tbl->lock){++-.}-{2:2}, at: neigh_managed_work+0x35/0x250 net/core/neighbour.c:1572 > #3: ffffffff8bb83ae0 (rcu_read_lock){....}-{1:2}, at: ip6_nd_hdr net/ipv6/ndisc.c:466 [inline] > #3: ffffffff8bb83ae0 (rcu_read_lock){....}-{1:2}, at: ndisc_send_skb+0x84b/0x17f0 net/ipv6/ndisc.c:502 > #4: ffffffff8bb83a80 (rcu_read_lock_bh){....}-{1:2}, at: lwtunnel_xmit_redirect include/net/lwtunnel.h:95 [inline] > #4: ffffffff8bb83a80 (rcu_read_lock_bh){....}-{1:2}, at: ip6_finish_output2+0x2ad/0x14f0 net/ipv6/ip6_output.c:112 > > stack backtrace: > CPU: 0 PID: 14617 Comm: kworker/0:16 Not tainted 5.17.0-rc1-syzkaller-00210-g6449520391df #0 > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 > Workqueue: events_power_efficient neigh_managed_work > Call Trace: > <TASK> > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0xcd/0x134 lib/dump_stack.c:106 > print_deadlock_bug kernel/locking/lockdep.c:2956 [inline] > check_deadlock kernel/locking/lockdep.c:2999 [inline] > validate_chain kernel/locking/lockdep.c:3788 [inline] > __lock_acquire.cold+0x149/0x3ab kernel/locking/lockdep.c:5027 > lock_acquire kernel/locking/lockdep.c:5639 [inline] > lock_acquire+0x1ab/0x510 kernel/locking/lockdep.c:5604 > __raw_write_lock_bh include/linux/rwlock_api_smp.h:202 [inline] > _raw_write_lock_bh+0x2f/0x40 kernel/locking/spinlock.c:334 > ___neigh_create+0x9e1/0x2990 net/core/neighbour.c:652 > ip6_finish_output2+0x1070/0x14f0 net/ipv6/ip6_output.c:123 > __ip6_finish_output net/ipv6/ip6_output.c:191 [inline] > __ip6_finish_output+0x61e/0xe90 net/ipv6/ip6_output.c:170 > ip6_finish_output+0x32/0x200 net/ipv6/ip6_output.c:201 > NF_HOOK_COND include/linux/netfilter.h:296 [inline] > ip6_output+0x1e4/0x530 net/ipv6/ip6_output.c:224 > dst_output include/net/dst.h:451 [inline] > NF_HOOK include/linux/netfilter.h:307 [inline] > ndisc_send_skb+0xa99/0x17f0 net/ipv6/ndisc.c:508 > ndisc_send_ns+0x3a9/0x840 net/ipv6/ndisc.c:650 > ndisc_solicit+0x2cd/0x4f0 net/ipv6/ndisc.c:742 > neigh_probe+0xc2/0x110 net/core/neighbour.c:1040 > __neigh_event_send+0x37d/0x1570 net/core/neighbour.c:1201 > neigh_event_send include/net/neighbour.h:470 [inline] > neigh_managed_work+0x162/0x250 net/core/neighbour.c:1574 > process_one_work+0x9ac/0x1650 kernel/workqueue.c:2307 > worker_thread+0x657/0x1110 kernel/workqueue.c:2454 > kthread+0x2e9/0x3a0 kernel/kthread.c:377 > ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295 > </TASK> > > > --- > This report is generated by a bot. It may contain errors. > See https://goo.gl/tpsmEJ for more information about syzbot. > syzbot engineers can be reached at syzkaller@googlegroups.com. > > syzbot will keep track of this issue. See: > https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
Probably caused by commit 7482e3841d520a368426ac196720601687e2dc47 net, neigh: Add NTF_MANAGED flag for managed neighbor entries
+static void neigh_managed_work(struct work_struct *work) +{ + struct neigh_table *tbl = container_of(work, struct neigh_table, + managed_work.work); + struct neighbour *neigh; + + write_lock_bh(&tbl->lock); + list_for_each_entry(neigh, &tbl->managed_list, managed_list) + neigh_event_send(neigh, NULL); // HERE
neigh_event_send() can need to lock tbl->lock, leading to a deadlock
+ queue_delayed_work(system_power_efficient_wq, &tbl->managed_work, + NEIGH_VAR(&tbl->parms, DELAY_PROBE_TIME)); + write_unlock_bh(&tbl->lock); +} +
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