possible deadlock in xt_find_revision

[syzbot]

Hello,

syzbot hit the following crash on net-next commit
6bb46bc57c8e9ce947cc605e555b7204b44d2b10 (Fri Jan 26 16:00:23 2018 +0000)
Merge branch 'cxgb4-fix-dump-collection-when-firmware-crashed'

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

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======================================================
WARNING: possible circular locking dependency detected
4.15.0-rc9+ #212 Not tainted
------------------------------------------------------
syz-executor5/5416 is trying to acquire lock:
(&xt[i].mutex){+.+.}, at: [<00000000f5db9e05>] xt_find_revision+0xc9/0x2b0
net/netfilter/x_tables.c:367

but task is already holding lock:
dccp_invalid_packet: P.Data Offset(66) too large
(sk_lock-AF_INET6){+.+.}, at: [<0000000049ab6b82>] lock_sock
include/net/sock.h:1463 [inline]
(sk_lock-AF_INET6){+.+.}, at: [<0000000049ab6b82>]
ipv6_getsockopt+0x1c5/0x2e0 net/ipv6/ipv6_sockglue.c:1377

which lock already depends on the new lock.

dccp_invalid_packet: P.Data Offset(66) too large

the existing dependency chain (in reverse order) is:

-> #2 (sk_lock-AF_INET6){+.+.}:
lock_sock_nested+0xc2/0x110 net/core/sock.c:2780
lock_sock include/net/sock.h:1463 [inline]
do_ipv6_setsockopt.isra.8+0x3c5/0x39d0 net/ipv6/ipv6_sockglue.c:167
ipv6_setsockopt+0xd7/0x150 net/ipv6/ipv6_sockglue.c:922
sctp_setsockopt+0x2b6/0x61d0 net/sctp/socket.c:4141
sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2978
SYSC_setsockopt net/socket.c:1849 [inline]
SyS_setsockopt+0x189/0x360 net/socket.c:1828
entry_SYSCALL_64_fastpath+0x29/0xa0

-> #1 (rtnl_mutex){+.+.}:
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74
unregister_netdevice_notifier+0x91/0x4e0 net/core/dev.c:1673
clusterip_config_entry_put net/ipv4/netfilter/ipt_CLUSTERIP.c:114
[inline]
clusterip_tg_destroy+0x389/0x6e0
net/ipv4/netfilter/ipt_CLUSTERIP.c:508
cleanup_entry+0x218/0x350 net/ipv4/netfilter/ip_tables.c:659
__do_replace+0x79d/0xa50 net/ipv4/netfilter/ip_tables.c:1094
do_replace net/ipv4/netfilter/ip_tables.c:1150 [inline]
do_ipt_set_ctl+0x40f/0x5f0 net/ipv4/netfilter/ip_tables.c:1680
nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
nf_setsockopt+0x67/0xc0 net/netfilter/nf_sockopt.c:115
ip_setsockopt+0xa1/0xb0 net/ipv4/ip_sockglue.c:1260
sctp_setsockopt+0x2b6/0x61d0 net/sctp/socket.c:4141
sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2978
SYSC_setsockopt net/socket.c:1849 [inline]
SyS_setsockopt+0x189/0x360 net/socket.c:1828
entry_SYSCALL_64_fastpath+0x29/0xa0

-> #0 (&xt[i].mutex){+.+.}:
lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3914
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
xt_find_revision+0xc9/0x2b0 net/netfilter/x_tables.c:367
do_ip6t_get_ctl+0x963/0xaf0 net/ipv6/netfilter/ip6_tables.c:1742
nf_sockopt net/netfilter/nf_sockopt.c:104 [inline]
nf_getsockopt+0x6a/0xc0 net/netfilter/nf_sockopt.c:122
ipv6_getsockopt+0x1df/0x2e0 net/ipv6/ipv6_sockglue.c:1378
tcp_getsockopt+0x82/0xd0 net/ipv4/tcp.c:3326
sock_common_getsockopt+0x95/0xd0 net/core/sock.c:2937
SYSC_getsockopt net/socket.c:1880 [inline]
SyS_getsockopt+0x178/0x340 net/socket.c:1862
entry_SYSCALL_64_fastpath+0x29/0xa0

other info that might help us debug this:

Chain exists of:
&xt[i].mutex --> rtnl_mutex --> sk_lock-AF_INET6

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(sk_lock-AF_INET6);
lock(rtnl_mutex);
lock(sk_lock-AF_INET6);
lock(&xt[i].mutex);

*** DEADLOCK ***

1 lock held by syz-executor5/5416:
#0: (sk_lock-AF_INET6){+.+.}, at: [<0000000049ab6b82>] lock_sock
include/net/sock.h:1463 [inline]
#0: (sk_lock-AF_INET6){+.+.}, at: [<0000000049ab6b82>]
ipv6_getsockopt+0x1c5/0x2e0 net/ipv6/ipv6_sockglue.c:1377

stack backtrace:
CPU: 1 PID: 5416 Comm: syz-executor5 Not tainted 4.15.0-rc9+ #212
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:17 [inline]
dump_stack+0x194/0x257 lib/dump_stack.c:53
print_circular_bug.isra.37+0x2cd/0x2dc kernel/locking/lockdep.c:1218
check_prev_add kernel/locking/lockdep.c:1858 [inline]
check_prevs_add kernel/locking/lockdep.c:1971 [inline]
validate_chain kernel/locking/lockdep.c:2412 [inline]
__lock_acquire+0x30a8/0x3e00 kernel/locking/lockdep.c:3426
lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3914
__mutex_lock_common kernel/locking/mutex.c:756 [inline]
__mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
xt_find_revision+0xc9/0x2b0 net/netfilter/x_tables.c:367
do_ip6t_get_ctl+0x963/0xaf0 net/ipv6/netfilter/ip6_tables.c:1742
nf_sockopt net/netfilter/nf_sockopt.c:104 [inline]
nf_getsockopt+0x6a/0xc0 net/netfilter/nf_sockopt.c:122
ipv6_getsockopt+0x1df/0x2e0 net/ipv6/ipv6_sockglue.c:1378
tcp_getsockopt+0x82/0xd0 net/ipv4/tcp.c:3326
sock_common_getsockopt+0x95/0xd0 net/core/sock.c:2937
SYSC_getsockopt net/socket.c:1880 [inline]
SyS_getsockopt+0x178/0x340 net/socket.c:1862
entry_SYSCALL_64_fastpath+0x29/0xa0
RIP: 0033:0x453299
RSP: 002b:00007f4ed20bec58 EFLAGS: 00000212 ORIG_RAX: 0000000000000037
RAX: ffffffffffffffda RBX: 000000000071bea0 RCX: 0000000000453299
RDX: 0000000000000045 RSI: 0000000000000029 RDI: 0000000000000013
RBP: 00000000000005ca R08: 0000000020000000 R09: 0000000000000000
R10: 0000000020ab2fe2 R11: 0000000000000212 R12: 00000000006f7b90
R13: 00000000ffffffff R14: 00007f4ed20bf6d4 R15: 0000000000000000
netlink: 'syz-executor7': attribute type 21 has an invalid length.
netlink: 'syz-executor7': attribute type 21 has an invalid length.


---
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[Florian Westphal]

#syz dup: possible deadlock in do_ip_getsockopt