syzbot

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)

======================================================
[ INFO: possible circular locking dependency detected ]
4.9.109-ga4230be #48 Not tainted
-------------------------------------------------------
syz-executor240/3796 is trying to acquire lock:
 (sk_lock-AF_INET){+.+.+.}, at: [<ffffffff8334669a>] lock_sock include/net/sock.h:1404 [inline]
 (sk_lock-AF_INET){+.+.+.}, at: [<ffffffff8334669a>] do_ip_setsockopt.isra.13+0x12a/0x2b10 net/ipv4/ip_sockglue.c:636
but task is already holding lock:
 (rtnl_mutex){+.+.+.}, at: [<ffffffff830b5937>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

       lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756
       __mutex_lock_common kernel/locking/mutex.c:521 [inline]
       mutex_lock_nested+0xc0/0x870 kernel/locking/mutex.c:621
       rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
       mrtsock_destruct+0x3b/0x1e0 net/ipv4/ipmr.c:1231
       ip_ra_control+0x2c2/0x420 net/ipv4/ip_sockglue.c:360
       do_ip_setsockopt.isra.13+0x15ff/0x2b10 net/ipv4/ip_sockglue.c:1137
       ip_setsockopt+0x3a/0xb0 net/ipv4/ip_sockglue.c:1240
       raw_setsockopt+0xb7/0xd0 net/ipv4/raw.c:833
       sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:2706
       SYSC_setsockopt net/socket.c:1772 [inline]
       SyS_setsockopt+0x166/0x260 net/socket.c:1751
       do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
       entry_SYSCALL_64_after_swapgs+0x5d/0xdb

       check_prev_add kernel/locking/lockdep.c:1828 [inline]
       check_prevs_add kernel/locking/lockdep.c:1938 [inline]
       validate_chain kernel/locking/lockdep.c:2265 [inline]
       __lock_acquire+0x3019/0x4070 kernel/locking/lockdep.c:3345
       lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756
       lock_sock_nested+0xc6/0x120 net/core/sock.c:2511
       lock_sock include/net/sock.h:1404 [inline]
       do_ip_setsockopt.isra.13+0x12a/0x2b10 net/ipv4/ip_sockglue.c:636
       ip_setsockopt+0x3a/0xb0 net/ipv4/ip_sockglue.c:1240
       udp_setsockopt+0x4a/0x90 net/ipv4/udp.c:2091
       sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:2706
       SYSC_setsockopt net/socket.c:1772 [inline]
       SyS_setsockopt+0x166/0x260 net/socket.c:1751
       do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
       entry_SYSCALL_64_after_swapgs+0x5d/0xdb

other info that might help us debug this:

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

1 lock held by syz-executor240/3796:
 #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff830b5937>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70

stack backtrace:
CPU: 1 PID: 3796 Comm: syz-executor240 Not tainted 4.9.109-ga4230be #48
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801da3b7758 ffffffff81eb3e29 ffffffff855e7b60 ffffffff8559cef0
 ffffffff855e7b60 ffff8801c81508e8 ffff8801c8150000 ffff8801da3b77a0
 ffffffff814262d4 0000000000000001 00000000c8150000 0000000000000001
Call Trace:
 [<ffffffff81eb3e29>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb3e29>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff814262d4>] print_circular_bug.cold.51+0x1bd/0x27d kernel/locking/lockdep.c:1202
 [<ffffffff81239179>] check_prev_add kernel/locking/lockdep.c:1828 [inline]
 [<ffffffff81239179>] check_prevs_add kernel/locking/lockdep.c:1938 [inline]
 [<ffffffff81239179>] validate_chain kernel/locking/lockdep.c:2265 [inline]
 [<ffffffff81239179>] __lock_acquire+0x3019/0x4070 kernel/locking/lockdep.c:3345
 [<ffffffff8123ac40>] lock_acquire+0x130/0x3e0 kernel/locking/lockdep.c:3756
 [<ffffffff830246a6>] lock_sock_nested+0xc6/0x120 net/core/sock.c:2511
 [<ffffffff8334669a>] lock_sock include/net/sock.h:1404 [inline]
 [<ffffffff8334669a>] do_ip_setsockopt.isra.13+0x12a/0x2b10 net/ipv4/ip_sockglue.c:636
 [<ffffffff833490ba>] ip_setsockopt+0x3a/0xb0 net/ipv4/ip_sockglue.c:1240
 [<ffffffff833f7b1a>] udp_setsockopt+0x4a/0x90 net/ipv4/udp.c:2091
 [<ffffffff8301d75a>] sock_common_setsockopt+0x9a/0xe0 net/core/sock.c:2706
 [<ffffffff8301a516>] SYSC_setsockopt net/socket.c:1772 [inline]
 [<ffffffff8301a516>] SyS_setsockopt+0x166/0x260 net/socket.c:1751