random: nonblocking pool is initialized
IPVS: Creating netns size=2552 id=1
device lo entered promiscuous mode

======================================================
[ INFO: possible circular locking dependency detected ]
4.4.141-g1b37d68 #7 Not tainted
-------------------------------------------------------
syz-executor0/3885 is trying to acquire lock:
 (rtnl_mutex){+.+.+.}, at: [<ffffffff82fb2787>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70

but task is already holding lock:
 (sk_lock-AF_INET6){+.+.+.}, at: [<ffffffff83480cad>] lock_sock include/net/sock.h:1493 [inline]
 (sk_lock-AF_INET6){+.+.+.}, at: [<ffffffff83480cad>] do_ipv6_setsockopt.isra.9+0x40d/0x32c0 net/ipv6/ipv6_sockglue.c:166

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

       [<ffffffff81235abe>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff82f26ae6>] lock_sock_nested+0xc6/0x120 net/core/sock.c:2459
       [<ffffffff83480c7a>] lock_sock include/net/sock.h:1493 [inline]
       [<ffffffff83480c7a>] do_ipv6_setsockopt.isra.9+0x3da/0x32c0 net/ipv6/ipv6_sockglue.c:166
       [<ffffffff83483d79>] compat_ipv6_setsockopt+0xe9/0x1d0 net/ipv6/ipv6_sockglue.c:935
       [<ffffffff8349282a>] compat_udpv6_setsockopt+0x4a/0x90 net/ipv6/udp.c:1446
       [<ffffffff82f24a84>] compat_sock_common_setsockopt+0xb4/0x150 net/core/sock.c:2670
       [<ffffffff8300b79c>] C_SYSC_setsockopt net/compat.c:385 [inline]
       [<ffffffff8300b79c>] compat_SyS_setsockopt+0x14c/0x2a0 net/compat.c:368
       [<ffffffff81006d96>] do_syscall_32_irqs_on arch/x86/entry/common.c:393 [inline]
       [<ffffffff81006d96>] do_fast_syscall_32+0x326/0x8b0 arch/x86/entry/common.c:460
       [<ffffffff838c456a>] sysenter_flags_fixed+0xd/0x17

       [<ffffffff81232972>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
       [<ffffffff81232972>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
       [<ffffffff81232972>] validate_chain kernel/locking/lockdep.c:2144 [inline]
       [<ffffffff81232972>] __lock_acquire+0x3902/0x5270 kernel/locking/lockdep.c:3213
       [<ffffffff81235abe>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
       [<ffffffff838bb26b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       [<ffffffff838bb26b>] mutex_lock_nested+0xbb/0x850 kernel/locking/mutex.c:621
       [<ffffffff82fb2787>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
       [<ffffffff834baf2e>] ipv6_sock_mc_close+0x10e/0x350 net/ipv6/mcast.c:288
       [<ffffffff8348317c>] do_ipv6_setsockopt.isra.9+0x28dc/0x32c0 net/ipv6/ipv6_sockglue.c:202
       [<ffffffff83483d79>] compat_ipv6_setsockopt+0xe9/0x1d0 net/ipv6/ipv6_sockglue.c:935
       [<ffffffff8349282a>] compat_udpv6_setsockopt+0x4a/0x90 net/ipv6/udp.c:1446
       [<ffffffff82f24a84>] compat_sock_common_setsockopt+0xb4/0x150 net/core/sock.c:2670
       [<ffffffff8300b79c>] C_SYSC_setsockopt net/compat.c:385 [inline]
       [<ffffffff8300b79c>] compat_SyS_setsockopt+0x14c/0x2a0 net/compat.c:368
       [<ffffffff81006d96>] do_syscall_32_irqs_on arch/x86/entry/common.c:393 [inline]
       [<ffffffff81006d96>] do_fast_syscall_32+0x326/0x8b0 arch/x86/entry/common.c:460
       [<ffffffff838c456a>] sysenter_flags_fixed+0xd/0x17

other info that might help us debug this:

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

1 lock held by syz-executor0/3885:
 #0:  (sk_lock-AF_INET6){+.+.+.}, at: [<ffffffff83480cad>] lock_sock include/net/sock.h:1493 [inline]
 #0:  (sk_lock-AF_INET6){+.+.+.}, at: [<ffffffff83480cad>] do_ipv6_setsockopt.isra.9+0x40d/0x32c0 net/ipv6/ipv6_sockglue.c:166

stack backtrace:
CPU: 1 PID: 3885 Comm: syz-executor0 Not tainted 4.4.141-g1b37d68 #7
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 216adb9cc45c9d0f ffff8801d9717588 ffffffff81e0e18d
 ffffffff8539cdf0 ffffffff853e4b20 ffffffff8539cdf0 ffff8800ac322100
 ffff8800ac321800 ffff8801d97175d0 ffffffff8140e71b 0000000000000001
Call Trace:
 [<ffffffff81e0e18d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e0e18d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff8140e71b>] print_circular_bug.cold.50+0x1bd/0x27d kernel/locking/lockdep.c:1226
 [<ffffffff81232972>] check_prev_add kernel/locking/lockdep.c:1853 [inline]
 [<ffffffff81232972>] check_prevs_add kernel/locking/lockdep.c:1958 [inline]
 [<ffffffff81232972>] validate_chain kernel/locking/lockdep.c:2144 [inline]
 [<ffffffff81232972>] __lock_acquire+0x3902/0x5270 kernel/locking/lockdep.c:3213
 [<ffffffff81235abe>] lock_acquire+0x15e/0x450 kernel/locking/lockdep.c:3592
 [<ffffffff838bb26b>] __mutex_lock_common kernel/locking/mutex.c:521 [inline]
 [<ffffffff838bb26b>] mutex_lock_nested+0xbb/0x850 kernel/locking/mutex.c:621
 [<ffffffff82fb2787>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
 [<ffffffff834baf2e>] ipv6_sock_mc_close+0x10e/0x350 net/ipv6/mcast.c:288
 [<ffffffff8348317c>] do_ipv6_setsockopt.isra.9+0x28dc/0x32c0 net/ipv6/ipv6_sockglue.c:202
 [<ffffffff83483d79>] compat_ipv6_setsockopt+0xe9/0x1d0 net/ipv6/ipv6_sockglue.c:935
 [<ffffffff8349282a>] compat_udpv6_setsockopt+0x4a/0x90 net/ipv6/udp.c:1446
 [<ffffffff82f24a84>] compat_sock_common_setsockopt+0xb4/0x150 net/core/sock.c:2670
 [<ffffffff8300b79c>] C_SYSC_setsockopt net/compat.c:385 [inline]
 [<ffffffff8300b79c>] compat_SyS_setsockopt+0x14c/0x2a0 net/compat.c:368
 [<ffffffff81006d96>] do_syscall_32_irqs_on arch/x86/entry/common.c:393 [inline]
 [<ffffffff81006d96>] do_fast_syscall_32+0x326/0x8b0 arch/x86/entry/common.c:460
 [<ffffffff838c456a>] sysenter_flags_fixed+0xd/0x17