======================================================
[ INFO: possible circular locking dependency detected ]
4.4.174+ #17 Not tainted
-------------------------------------------------------
syz-executor.1/7646 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
       [<ffffffff826000da>] lock_sock include/net/sock.h:1497 [inline]
       [<ffffffff826000da>] do_ipv6_setsockopt.isra.0+0x2eba/0x30c0 net/ipv6/ipv6_sockglue.c:166
       [<ffffffff826003ba>] ipv6_setsockopt+0xda/0x140 net/ipv6/ipv6_sockglue.c:904
       [<ffffffff822aa357>] compat_mc_setsockopt+0x4f7/0x690 net/compat.c:630
       [<ffffffff82600544>] compat_ipv6_setsockopt net/ipv6/ipv6_sockglue.c:932 [inline]
       [<ffffffff82600544>] compat_ipv6_setsockopt+0x124/0x1d0 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

       [<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
       [  179.293282] audit: type=1400 audit(1556509556.026:316): avc:  denied  { create } for  pid=7597 comm="syz-executor.4" 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=0
[<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.1/7646:
 #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: 1 PID: 7646 Comm: syz-executor.1 Not tainted 4.4.174+ #17
 0000000000000000 bcfa9b0c7af10279 ffff8801d549f540 ffffffff81aad1a1
 ffffffff84057a80 ffff8800b32e97c0 ffffffff83a8db50 ffffffff83acc760
 ffffffff83a8db50 ffff8801d549f590 ffffffff813abcda ffff8801d549f670
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
audit: type=1400 audit(1556509556.786:317): avc:  denied  { set_context_mgr } for  pid=7672 comm="syz-executor.0" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tclass=binder permissive=0
binder: 7672:7686 unknown command 1074029312
binder: 7672:7686 ioctl c0306201 20000680 returned -22
binder: 7672:7676 ioctl 40046207 0 returned -13
audit: type=1400 audit(1556509556.906:318): avc:  denied  { create } for  pid=7694 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=0
audit: type=1400 audit(1556509556.906:319): avc:  denied  { create } for  pid=7664 comm="syz-executor.4" 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=0
binder: 7672:7676 ioctl 40046207 0 returned -13
binder: 7672:7686 unknown command 1074029312
binder: 7672:7686 ioctl c0306201 20000680 returned -22
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=2665 sclass=netlink_route_socket
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=2665 sclass=netlink_route_socket
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=2665 sclass=netlink_route_socket
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=2665 sclass=netlink_route_socket
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=2665 sclass=netlink_route_socket
audit_printk_skb: 21 callbacks suppressed
audit: type=1400 audit(1556509559.956:328): avc:  denied  { create } for  pid=7765 comm="syz-executor.4" 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=0
audit: type=1400 audit(1556509559.946:327): avc:  denied  { create } for  pid=7780 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=0
audit: type=1400 audit(1556509560.016:329): avc:  denied  { create } for  pid=7762 comm="syz-executor.2" 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=0
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=2665 sclass=netlink_route_socket
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=2665 sclass=netlink_route_socket
audit: type=1400 audit(1556509560.286:330): avc:  denied  { create } for  pid=7792 comm="syz-executor.4" 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=0
audit: type=1400 audit(1556509562.996:331): avc:  denied  { create } for  pid=7837 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=0
audit: type=1400 audit(1556509562.996:332): avc:  denied  { create } for  pid=7817 comm="syz-executor.4" 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=0
audit: type=1400 audit(1556509563.176:333): avc:  denied  { create } for  pid=7820 comm="syz-executor.2" 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=0