Hi,
I've got the following error report while fuzzing the kernel with syzkaller.
On commit c470abd4fde40ea6a0846a2beab642a578c0b8cd (4.10).
Unfortunately I can't reproduce it.
======================================================
[ INFO: possible circular locking dependency detected ]
4.10.0-rc8+ #201 Not tainted
-------------------------------------------------------
kworker/0:2/1404 is trying to acquire lock:
(&(&list->lock)->rlock#3){+.-...}, at: [<ffffffff8335b23f>]
skb_queue_tail+0xcf/0x2f0 net/core/skbuff.c:2478
but task is already holding lock:
(&(&pcpu->lock)->rlock){+.-...}, at: [<ffffffff8366b55f>] spin_lock
include/linux/spinlock.h:302 [inline]
(&(&pcpu->lock)->rlock){+.-...}, at: [<ffffffff8366b55f>]
ecache_work_evict_list+0xaf/0x590
net/netfilter/nf_conntrack_ecache.c:48
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&(&pcpu->lock)->rlock){+.-...}:
validate_chain kernel/locking/lockdep.c:2265 [inline]
__lock_acquire+0x20a7/0x3270 kernel/locking/lockdep.c:3338
lock_acquire+0x241/0x580 kernel/locking/lockdep.c:3753
__raw_spin_lock include/linux/spinlock_api_smp.h:144 [inline]
_raw_spin_lock+0x33/0x50 kernel/locking/spinlock.c:151
spin_lock include/linux/spinlock.h:302 [inline]
nf_ct_del_from_dying_or_unconfirmed_list+0x10e/0x2f0
net/netfilter/nf_conntrack_core.c:347
destroy_conntrack+0x261/0x430 net/netfilter/nf_conntrack_core.c:409
nf_conntrack_destroy+0x107/0x240 net/netfilter/core.c:398
nf_conntrack_put include/linux/skbuff.h:3561 [inline]
skb_release_head_state+0x19e/0x250 net/core/skbuff.c:658
skb_release_all+0x15/0x60 net/core/skbuff.c:668
__kfree_skb+0x15/0x20 net/core/skbuff.c:684
kfree_skb+0x16e/0x4e0 net/core/skbuff.c:705
kfree_skb_list net/core/skbuff.c:714 [inline]
skb_release_data+0x38e/0x470 net/core/skbuff.c:609
skb_release_all+0x4a/0x60 net/core/skbuff.c:670
__kfree_skb+0x15/0x20 net/core/skbuff.c:684
kfree_skb+0x16e/0x4e0 net/core/skbuff.c:705
first_packet_length+0x3c4/0x6e0 net/ipv4/udp.c:1376
udp_poll+0x423/0x550 net/ipv4/udp.c:2343
sock_poll+0x1ae/0x210 net/socket.c:1051
do_pollfd fs/select.c:781 [inline]
do_poll fs/select.c:831 [inline]
do_sys_poll+0x8a6/0x1340 fs/select.c:925
SYSC_poll fs/select.c:983 [inline]
SyS_poll+0x147/0x490 fs/select.c:971
entry_SYSCALL_64_fastpath+0x1f/0xc2
-> #0 (&(&list->lock)->rlock#3){+.-...}:
check_prev_add kernel/locking/lockdep.c:1828 [inline]
check_prevs_add+0xaad/0x1a10 kernel/locking/lockdep.c:1938
validate_chain kernel/locking/lockdep.c:2265 [inline]
__lock_acquire+0x20a7/0x3270 kernel/locking/lockdep.c:3338
lock_acquire+0x241/0x580 kernel/locking/lockdep.c:3753
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:112 [inline]
_raw_spin_lock_irqsave+0xc9/0x110 kernel/locking/spinlock.c:159
skb_queue_tail+0xcf/0x2f0 net/core/skbuff.c:2478
__netlink_sendskb+0x58/0xa0 net/netlink/af_netlink.c:1177
netlink_broadcast_deliver net/netlink/af_netlink.c:1302 [inline]
do_one_broadcast net/netlink/af_netlink.c:1386 [inline]
netlink_broadcast_filtered+0xe26/0x1420 net/netlink/af_netlink.c:1430
netlink_broadcast net/netlink/af_netlink.c:1454 [inline]
nlmsg_multicast include/net/netlink.h:576 [inline]
nlmsg_notify+0xa2/0x140 net/netlink/af_netlink.c:2341
nfnetlink_send+0x63/0x80 net/netfilter/nfnetlink.c:133
ctnetlink_conntrack_event+0x10b3/0x1720
net/netfilter/nf_conntrack_netlink.c:740
nf_conntrack_eventmask_report+0x61b/0x850
net/netfilter/nf_conntrack_ecache.c:149
nf_conntrack_event
include/net/netfilter/nf_conntrack_ecache.h:122 [inline]
ecache_work_evict_list+0x33e/0x590 net/netfilter/nf_conntrack_ecache.c:61
ecache_work+0xf2/0x220 net/netfilter/nf_conntrack_ecache.c:98
process_one_work+0xc06/0x1c20 kernel/workqueue.c:2098
worker_thread+0x223/0x19c0 kernel/workqueue.c:2232
kthread+0x326/0x3f0 kernel/kthread.c:227
ret_from_fork+0x31/0x40 arch/x86/entry/entry_64.S:430
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&(&pcpu->lock)->rlock);
lock(&(&list->lock)->rlock#3);
lock(&(&pcpu->lock)->rlock);
lock(&(&list->lock)->rlock#3);
*** DEADLOCK ***
4 locks held by kworker/0:2/1404:
#0: ("events"){.+.+.+}, at: [<ffffffff8133a239>] __write_once_size
include/linux/compiler.h:272 [inline]
#0: ("events"){.+.+.+}, at: [<ffffffff8133a239>] atomic64_set
arch/x86/include/asm/atomic64_64.h:33 [inline]
#0: ("events"){.+.+.+}, at: [<ffffffff8133a239>] atomic_long_set
include/asm-generic/atomic-long.h:56 [inline]
#0: ("events"){.+.+.+}, at: [<ffffffff8133a239>] set_work_data
kernel/workqueue.c:617 [inline]
#0: ("events"){.+.+.+}, at: [<ffffffff8133a239>]
set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
#0: ("events"){.+.+.+}, at: [<ffffffff8133a239>]
process_one_work+0xae9/0x1c20 kernel/workqueue.c:2091
#1: ((&(&net->ct.ecache_dwork)->work)){+.+...}, at:
[<ffffffff8133a28d>] process_one_work+0xb3d/0x1c20
kernel/workqueue.c:2095
#2: (&(&pcpu->lock)->rlock){+.-...}, at: [<ffffffff8366b55f>]
spin_lock include/linux/spinlock.h:302 [inline]
#2: (&(&pcpu->lock)->rlock){+.-...}, at: [<ffffffff8366b55f>]
ecache_work_evict_list+0xaf/0x590
net/netfilter/nf_conntrack_ecache.c:48
#3: (rcu_read_lock){......}, at: [<ffffffff8366ad08>] read_pnet
include/net/net_namespace.h:260 [inline]
#3: (rcu_read_lock){......}, at: [<ffffffff8366ad08>] nf_ct_net
include/net/netfilter/nf_conntrack.h:153 [inline]
#3: (rcu_read_lock){......}, at: [<ffffffff8366ad08>]
nf_conntrack_eventmask_report+0xa8/0x850
net/netfilter/nf_conntrack_ecache.c:124
stack backtrace:
CPU: 0 PID: 1404 Comm: kworker/0:2 Not tainted 4.10.0-rc8+ #201
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
Workqueue: events ecache_work
Call Trace:
__dump_stack lib/dump_stack.c:15 [inline]
dump_stack+0x292/0x398 lib/dump_stack.c:51
print_circular_bug+0x310/0x3c0 kernel/locking/lockdep.c:1202
check_prev_add kernel/locking/lockdep.c:1828 [inline]
check_prevs_add+0xaad/0x1a10 kernel/locking/lockdep.c:1938
validate_chain kernel/locking/lockdep.c:2265 [inline]
__lock_acquire+0x20a7/0x3270 kernel/locking/lockdep.c:3338
lock_acquire+0x241/0x580 kernel/locking/lockdep.c:3753
__raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:112 [inline]
_raw_spin_lock_irqsave+0xc9/0x110 kernel/locking/spinlock.c:159
skb_queue_tail+0xcf/0x2f0 net/core/skbuff.c:2478
__netlink_sendskb+0x58/0xa0 net/netlink/af_netlink.c:1177
netlink_broadcast_deliver net/netlink/af_netlink.c:1302 [inline]
do_one_broadcast net/netlink/af_netlink.c:1386 [inline]
netlink_broadcast_filtered+0xe26/0x1420 net/netlink/af_netlink.c:1430
netlink_broadcast net/netlink/af_netlink.c:1454 [inline]
nlmsg_multicast include/net/netlink.h:576 [inline]
nlmsg_notify+0xa2/0x140 net/netlink/af_netlink.c:2341
nfnetlink_send+0x63/0x80 net/netfilter/nfnetlink.c:133
ctnetlink_conntrack_event+0x10b3/0x1720
net/netfilter/nf_conntrack_netlink.c:740
nf_conntrack_eventmask_report+0x61b/0x850
net/netfilter/nf_conntrack_ecache.c:149
nf_conntrack_event include/net/netfilter/nf_conntrack_ecache.h:122 [inline]
ecache_work_evict_list+0x33e/0x590 net/netfilter/nf_conntrack_ecache.c:61
ecache_work+0xf2/0x220 net/netfilter/nf_conntrack_ecache.c:98
process_one_work+0xc06/0x1c20 kernel/workqueue.c:2098
worker_thread+0x223/0x19c0 kernel/workqueue.c:2232
kthread+0x326/0x3f0 kernel/kthread.c:227
ret_from_fork+0x31/0x40 arch/x86/entry/entry_64.S:430
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