random: sshd: uninitialized urandom read (32 bytes read, 120 bits of entropy available)
random: sshd: uninitialized urandom read (32 bytes read, 123 bits of entropy available)
random: nonblocking pool is initialized

======================================================
[ INFO: possible circular locking dependency detected ]
4.4.141-g1b37d68 #71 Not tainted
-------------------------------------------------------
syz-executor209/3832 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
       [<ffffffff83483bf7>] ipv6_setsockopt+0x97/0x130 net/ipv6/ipv6_sockglue.c:904
       [<ffffffff8349295a>] udpv6_setsockopt+0x4a/0x90 net/ipv6/udp.c:1436
       [<ffffffff82f2498a>] sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:2659
       [<ffffffff82f218a6>] SYSC_setsockopt net/socket.c:1767 [inline]
       [<ffffffff82f218a6>] SyS_setsockopt+0x166/0x260 net/socket.c:1746
       [<ffffffff838c2c25>] entry_SYSCALL_64_fastpath+0x22/0x9e

       [<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
       [<ffffffff83483bf7>] ipv6_setsockopt+0x97/0x130 net/ipv6/ipv6_sockglue.c:904
       [<ffffffff8349295a>] udpv6_setsockopt+0x4a/0x90 net/ipv6/udp.c:1436
       [<ffffffff82f2498a>] sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:2659
       [<ffffffff82f218a6>] SYSC_setsockopt net/socket.c:1767 [inline]
       [<ffffffff82f218a6>] SyS_setsockopt+0x166/0x260 net/socket.c:1746
       [<ffffffff838c2c25>] entry_SYSCALL_64_fastpath+0x22/0x9e

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-executor209/3832:
 #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: 3832 Comm: syz-executor209 Not tainted 4.4.141-g1b37d68 #71
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 0000000000000000 c4204f1a20bd06c5 ffff8801d37f75b8 ffffffff81e0e18d
 ffffffff8539cdf0 ffffffff853e4610 ffffffff8539cdf0 ffff8800acd4d100
 ffff8800acd4c800 ffff8801d37f7600 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
 [<ffffffff83483bf7>] ipv6_setsockopt+0x97/0x130 net/ipv6/ipv6_sockglue.c:904
 [<ffffffff8349295a>] udpv6_setsockopt+0x4a/0x90 net/ipv6/udp.c:1436
 [<ffffffff82f2498a>] sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:2659
 [<ffffffff82f218a6>] SYSC_setsockopt net/socket.c:1767 [inline]
 [<ffffffff82f218a6>] SyS_setsockopt+0x166/0x260 net/socket.c:1746
 [<fffff