======================================================
[ INFO: possible circular locking dependency detected ]
audit: type=1400 audit(1563708210.749:46): avc:  denied  { bind } for  pid=12804 comm="syz-executor.1" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=netlink_generic_socket permissive=1
4.4.174+ #17 Not tainted
-------------------------------------------------------
syz-executor.2/12800 is trying to acquire lock:
 (rtnl_mutex){+.+.+.}, at: [<ffffffff8226e537>] rtnl_lock+0x17/0x20 /net/core/rtnetlink.c:70

but task is already holding lock:
 (sk_lock-AF_INET6){+.+.+.}, at: [<ffffffff825fd4aa>] lock_sock /include/net/sock.h:1497 [inline]
 (sk_lock-AF_INET6){+.+.+.}, at: [<ffffffff825fd4aa>] do_ipv6_setsockopt.isra.0+0x28a/0x30c0 /net/ipv6/ipv6_sockglue.c:166

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

       [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 /kernel/locking/lockdep.c:3592
       [<ffffffff821e4f06>] lock_sock_nested+0xc6/0x120 /net/core/sock.c:2463
       [<ffffffff823d7370>] lock_sock /include/net/sock.h:1497 [inline]
       [<ffffffff823d7370>] do_ip_setsockopt.isra.0+0x100/0x33a0 /net/ipv4/ip_sockglue.c:625
       [<ffffffff823da64b>] ip_setsockopt+0x3b/0xa0 /net/ipv4/ip_sockglue.c:1218
       [<ffffffff822aa357>] compat_mc_setsockopt+0x4f7/0x690 /net/compat.c:630
       [<ffffffff823da772>] compat_ip_setsockopt+0xc2/0xd0 /net/ipv4/ip_sockglue.c:1241
       [<ffffffff8248026e>] compat_udp_setsockopt+0x4e/0x90 /net/ipv4/udp.c:2172
       [<ffffffff826004d4>] compat_ipv6_setsockopt+0xb4/0x1d0 /net/ipv6/ipv6_sockglue.c:923
       [<ffffffff823e3719>] inet_csk_compat_setsockopt+0x99/0x120 /net/ipv4/inet_connection_sock.c:914
       [<ffffffff823f7770>] compat_tcp_setsockopt+0x40/0x70 /net/ipv4/tcp.c:2654
       [<ffffffff821df024>] compat_sock_common_setsockopt+0xb4/0x150 /net/core/sock.c:2674
       [<ffffffff822ac2ac>] C_SYSC_setsockopt /net/compat.c:385 [inline]
       [<ffffffff822ac2ac>] compat_SyS_setsockopt+0x15c/0x720 /net/compat.c:368
       [<ffffffff8100603d>] do_syscall_32_irqs_on /arch/x86/entry/common.c:330 [inline]
       [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 /arch/x86/entry/common.c:397
       [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a

       [<ffffffff81202d86>] check_prev_add /kernel/locking/lockdep.c:1853 [inline]
       [<ffffffff81202d86>] check_prevs_add /kernel/locking/lockdep.c:1958 [inline]
       [<ffffffff81202d86>] validate_chain /kernel/locking/lockdep.c:2144 [inline]
       [<ffffffff81202d86>] __lock_acquire+0x37d6/0x4f50 /kernel/locking/lockdep.c:3213
       [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 /kernel/locking/lockdep.c:3592
       [<ffffffff8270c191>] __mutex_lock_common /kernel/locking/mutex.c:521 [inline]
       [<ffffffff8270c191>] mutex_lock_nested+0xc1/0xb80 /kernel/locking/mutex.c:621
       [<ffffffff8226e537>] rtnl_lock+0x17/0x20 /net/core/rtnetlink.c:70
       [<ffffffff826369ee>] ipv6_sock_mc_close+0x10e/0x350 /net/ipv6/mcast.c:288
       [<ffffffff825fedf1>] do_ipv6_setsockopt.isra.0+0x1bd1/0x30c0 /net/ipv6/ipv6_sockglue.c:202
       [<ffffffff82600507>] compat_ipv6_setsockopt /net/ipv6/ipv6_sockglue.c:935 [inline]
       [<ffffffff82600507>] compat_ipv6_setsockopt+0xe7/0x1d0 /net/ipv6/ipv6_sockglue.c:916
       [<ffffffff82614b4e>] compat_udpv6_setsockopt+0x4e/0x90 /net/ipv6/udp.c:1446
       [<ffffffff821df024>] compat_sock_common_setsockopt+0xb4/0x150 /net/core/sock.c:2674
       [<ffffffff822ac2ac>] C_SYSC_setsockopt /net/compat.c:385 [inline]
       [<ffffffff822ac2ac>] compat_SyS_setsockopt+0x15c/0x720 /net/compat.c:368
       [<ffffffff8100603d>] do_syscall_32_irqs_on /arch/x86/entry/common.c:330 [inline]
       [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 /arch/x86/entry/common.c:397
       [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a

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-executor.2/12800:
 #0:  (sk_lock-AF_INET6){+.+.+.}, at: [<ffffffff825fd4aa>] lock_sock /include/net/sock.h:1497 [inline]
 #0:  (sk_lock-AF_INET6){+.+.+.}, at: [<ffffffff825fd4aa>] do_ipv6_setsockopt.isra.0+0x28a/0x30c0 /net/ipv6/ipv6_sockglue.c:166

stack backtrace:
CPU: 0 PID: 12800 Comm: syz-executor.2 Not tainted 4.4.174+ #17
 0000000000000000 baf8ac3ea203b56a ffff8801d2c37540 ffffffff81aad1a1
 ffffffff84057a80 ffff8801d2ae4740 ffffffff83a8db50 ffffffff83acc760
 ffffffff83a8db50 ffff8801d2c37590 ffffffff813abcda ffff8801d2c37670
Call Trace:
 [<ffffffff81aad1a1>] __dump_stack /lib/dump_stack.c:15 [inline]
 [<ffffffff81aad1a1>] dump_stack+0xc1/0x120 /lib/dump_stack.c:51
 [<ffffffff813abcda>] print_circular_bug.cold+0x2f7/0x44e /kernel/locking/lockdep.c:1226
 [<ffffffff81202d86>] check_prev_add /kernel/locking/lockdep.c:1853 [inline]
 [<ffffffff81202d86>] check_prevs_add /kernel/locking/lockdep.c:1958 [inline]
 [<ffffffff81202d86>] validate_chain /kernel/locking/lockdep.c:2144 [inline]
 [<ffffffff81202d86>] __lock_acquire+0x37d6/0x4f50 /kernel/locking/lockdep.c:3213
 [<ffffffff81205f6e>] lock_acquire+0x15e/0x450 /kernel/locking/lockdep.c:3592
 [<ffffffff8270c191>] __mutex_lock_common /kernel/locking/mutex.c:521 [inline]
 [<ffffffff8270c191>] mutex_lock_nested+0xc1/0xb80 /kernel/locking/mutex.c:621
 [<ffffffff8226e537>] rtnl_lock+0x17/0x20 /net/core/rtnetlink.c:70
 [<ffffffff826369ee>] ipv6_sock_mc_close+0x10e/0x350 /net/ipv6/mcast.c:288
 [<ffffffff825fedf1>] do_ipv6_setsockopt.isra.0+0x1bd1/0x30c0 /net/ipv6/ipv6_sockglue.c:202
 [<ffffffff82600507>] compat_ipv6_setsockopt /net/ipv6/ipv6_sockglue.c:935 [inline]
 [<ffffffff82600507>] compat_ipv6_setsockopt+0xe7/0x1d0 /net/ipv6/ipv6_sockglue.c:916
 [<ffffffff82614b4e>] compat_udpv6_setsockopt+0x4e/0x90 /net/ipv6/udp.c:1446
 [<ffffffff821df024>] compat_sock_common_setsockopt+0xb4/0x150 /net/core/sock.c:2674
 [<ffffffff822ac2ac>] C_SYSC_setsockopt /net/compat.c:385 [inline]
 [<ffffffff822ac2ac>] compat_SyS_setsockopt+0x15c/0x720 /net/compat.c:368
 [<ffffffff8100603d>] do_syscall_32_irqs_on /arch/x86/entry/common.c:330 [inline]
 [<ffffffff8100603d>] do_fast_syscall_32+0x32d/0xa90 /arch/x86/entry/common.c:397
 [<ffffffff8271a350>] sysenter_flags_fixed+0xd/0x1a