Subject: suspicious RCU usage at ./include/net/inet_sock.h:LINE

From: syzbot <[email-masked]>
Date: Mon, 25 Dec 2017 17:45:00 -0800

syzkaller has found reproducer for the following crash on  
fba961ab29e5ffb055592442808bb0f7962e05da
git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers

Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable

=============================
WARNING: suspicious RCU usage
4.15.0-rc4+ #164 Not tainted
-----------------------------
./include/net/inet_sock.h:136 suspicious rcu_dereference_check() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syzkaller667189/5780:
  #0:  (sk_lock-AF_INET6){+.+.}, at: [<000000008d7d4e62>] lock_sock  
include/net/sock.h:1462 [inline]
  #0:  (sk_lock-AF_INET6){+.+.}, at: [<000000008d7d4e62>]  
do_ipv6_setsockopt.isra.9+0x23d/0x38f0 net/ipv6/ipv6_sockglue.c:167

stack backtrace:
CPU: 0 PID: 5780 Comm: syzkaller667189 Not tainted 4.15.0-rc4+ #164
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x194/0x257 lib/dump_stack.c:53
  lockdep_rcu_suspicious+0x123/0x170 kernel/locking/lockdep.c:4585
  ireq_opt_deref include/net/inet_sock.h:135 [inline]
  inet_csk_route_req+0x824/0xca0 net/ipv4/inet_connection_sock.c:544
  dccp_v4_send_response+0xa7/0x640 net/dccp/ipv4.c:485
  dccp_v4_conn_request+0x9ee/0x11b0 net/dccp/ipv4.c:633
  dccp_v6_conn_request+0xd30/0x1350 net/dccp/ipv6.c:317
  dccp_rcv_state_process+0x574/0x1620 net/dccp/input.c:612
  dccp_v4_do_rcv+0xeb/0x160 net/dccp/ipv4.c:682
  dccp_v6_do_rcv+0x81a/0x9b0 net/dccp/ipv6.c:578
  sk_backlog_rcv include/net/sock.h:907 [inline]
  __release_sock+0x124/0x360 net/core/sock.c:2274
  release_sock+0xa4/0x2a0 net/core/sock.c:2789
  do_ipv6_setsockopt.isra.9+0x50f/0x38f0 net/ipv6/ipv6_sockglue.c:898
  ipv6_setsockopt+0xd7/0x150 net/ipv6/ipv6_sockglue.c:922
  dccp_setsockopt+0x85/0xd0 net/dccp/proto.c:573
  sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2978
  SYSC_setsockopt net/socket.c:1821 [inline]
  SyS_setsockopt+0x189/0x360 net/socket.c:1800
  entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x445ec9
RSP: 002b:00007fa001b58db8 EFLAGS: 00000297 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00000000006dbc24 RCX: 0000000000445ec9
RDX: 0000000000000020 RSI: 0000000000000029 RDI: 0000000000000004
RBP: 00000000006dbc20 R08: 0000000000000020 R09: 0000000000000000
R10: 000000002030a000 R11: 0000000000000297 R12: 0000000000000000
R13: 00007fff809eec1f R14: 00007fa001b599c0 R15: 0000000000000001

=============================
WARNING: suspicious RCU usage
4.15.0-rc4+ #164 Not tainted
-----------------------------
./include/net/inet_sock.h:136 suspicious rcu_dereference_check() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
1 lock held by syzkaller667189/5780:
  #0:  (sk_lock-AF_INET6){+.+.}, at: [<000000008d7d4e62>] lock_sock  
include/net/sock.h:1462 [inline]
  #0:  (sk_lock-AF_INET6){+.+.}, at: [<000000008d7d4e62>]  
do_ipv6_setsockopt.isra.9+0x23d/0x38f0 net/ipv6/ipv6_sockglue.c:167

stack backtrace:
CPU: 0 PID: 5780 Comm: syzkaller667189 Not tainted 4.15.0-rc4+ #164
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
  __dump_stack lib/dump_stack.c:17 [inline]
  dump_stack+0x194/0x257 lib/dump_stack.c:53
  lockdep_rcu_suspicious+0x123/0x170 kernel/locking/lockdep.c:4585
  ireq_opt_deref include/net/inet_sock.h:135 [inline]
  dccp_v4_send_response+0x4b0/0x640 net/dccp/ipv4.c:496
  dccp_v4_conn_request+0x9ee/0x11b0 net/dccp/ipv4.c:633
  dccp_v6_conn_request+0xd30/0x1350 net/dccp/ipv6.c:317
  dccp_rcv_state_process+0x574/0x1620 net/dccp/input.c:612
  dccp_v4_do_rcv+0xeb/0x160 net/dccp/ipv4.c:682
  dccp_v6_do_rcv+0x81a/0x9b0 net/dccp/ipv6.c:578
  sk_backlog_rcv include/net/sock.h:907 [inline]
  __release_sock+0x124/0x360 net/core/sock.c:2274
  release_sock+0xa4/0x2a0 net/core/sock.c:2789
  do_ipv6_setsockopt.isra.9+0x50f/0x38f0 net/ipv6/ipv6_sockglue.c:898
  ipv6_setsockopt+0xd7/0x150 net/ipv6/ipv6_sockglue.c:922
  dccp_setsockopt+0x85/0xd0 net/dccp/proto.c:573
  sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2978
  SYSC_setsockopt net/socket.c:1821 [inline]
  SyS_setsockopt+0x189/0x360 net/socket.c:1800
  entry_SYSCALL_64_fastpath+0x1f/0x96
RIP: 0033:0x445ec9
RSP: 002b:00007fa001b58db8 EFLAGS: 00000297 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00000000006dbc24 RCX: 0000000000445ec9
RDX: 0000000000000020 RSI: 0000000000000029 RDI: 0000000000000004
RBP: 00000000006dbc20 R08: 0000000000000020 R09: 0000000000000000
R10: 000000002030a000 R11: 0000000000000297 R12: 0000000000000000
R13: 00007fff809eec1f R14: 00007fa001b599c0 R15: 0000000000000001
net_ratelimit: 986 callbacks suppressed
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
net_ratelimit: 1063 callbacks suppressed
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable
Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable