possible deadlock in do_ipv6_setsockopt

[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'

So far this crash happened 3 times on net-next, upstream.
C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.

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audit: type=1400 audit(1517071608.831:7): avc: denied { map } for
pid=3682 comm="syzkaller041579" path="/root/syzkaller041579251" dev="sda1"
ino=16481 scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023
tcontext=unconfined_u:object_r:user_home_t:s0 tclass=file permissive=1

======================================================
WARNING: possible circular locking dependency detected
4.15.0-rc9+ #212 Not tainted
------------------------------------------------------
syzkaller041579/3682 is trying to acquire lock:
(sk_lock-AF_INET6){+.+.}, at: [<000000008775e4dd>] lock_sock
include/net/sock.h:1463 [inline]
(sk_lock-AF_INET6){+.+.}, at: [<000000008775e4dd>]
do_ipv6_setsockopt.isra.8+0x3c5/0x39d0 net/ipv6/ipv6_sockglue.c:167

but task is already holding lock:
(rtnl_mutex){+.+.}, at: [<000000004342eaa9>] rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #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
register_netdevice_notifier+0xad/0x860 net/core/dev.c:1607
tee_tg_check+0x1a0/0x280 net/netfilter/xt_TEE.c:106
xt_check_target+0x22c/0x7d0 net/netfilter/x_tables.c:845
check_target net/ipv6/netfilter/ip6_tables.c:538 [inline]
find_check_entry.isra.7+0x935/0xcf0
net/ipv6/netfilter/ip6_tables.c:580
translate_table+0xf52/0x1690 net/ipv6/netfilter/ip6_tables.c:749
do_replace net/ipv6/netfilter/ip6_tables.c:1165 [inline]
do_ip6t_set_ctl+0x370/0x5f0 net/ipv6/netfilter/ip6_tables.c:1691
nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
nf_setsockopt+0x67/0xc0 net/netfilter/nf_sockopt.c:115
ipv6_setsockopt+0x115/0x150 net/ipv6/ipv6_sockglue.c:928
udpv6_setsockopt+0x45/0x80 net/ipv6/udp.c:1422
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 (sk_lock-AF_INET6){+.+.}:
lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3914
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
udpv6_setsockopt+0x45/0x80 net/ipv6/udp.c:1422
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

other info that might help us debug this:

Possible unsafe locking scenario:

CPU0 CPU1
---- ----
lock(rtnl_mutex);
lock(sk_lock-AF_INET6);
lock(rtnl_mutex);
lock(sk_lock-AF_INET6);

*** DEADLOCK ***

1 lock held by syzkaller041579/3682:
#0: (rtnl_mutex){+.+.}, at: [<000000004342eaa9>] rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74

stack backtrace:
CPU: 1 PID: 3682 Comm: syzkaller041579 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
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
udpv6_setsockopt+0x45/0x80 net/ipv6/udp.c:1422
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
RIP: 0033:0x4411d9
RSP: 002b:00007ffc60dba938 EFLAGS: 00000207 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: ffffffffffffffff RCX: 00000000004411d9
RDX: 000000000000002d RSI: 0000000000000029 RDI: 0000000000000004
RBP: 00000000006cb018 R08: 0000000000000088 R09: 0000000000000000
R10: 0000000020d01f78 R11: 0000000000000207 R12: 0000000000402b00
R13: 00000000


---
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[Florian Westphal]

#syz dup: possible deadlock in do_ip_getsockopt