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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "stable@vger.kernel.org" <stable@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
CC:     Xin Long <lucien.xin@gmail.com>,
        "David S . Miller" <davem@davemloft.net>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.9 028/293] sctp: fix recursive locking warning
 in sctp_do_peeloff
Thread-Topic: [PATCH AUTOSEL for 4.9 028/293] sctp: fix recursive locking
 warning in sctp_do_peeloff
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Date:   Mon, 9 Apr 2018 00:23:12 +0000
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From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit 6dfe4b97e08ec3d1a593fdaca099f0ef0a3a19e6 ]

Dmitry got the following recursive locking report while running syzkaller
fuzzer, the Call Trace:
 __dump_stack lib/dump_stack.c:16 [inline]
 dump_stack+0x2ee/0x3ef lib/dump_stack.c:52
 print_deadlock_bug kernel/locking/lockdep.c:1729 [inline]
 check_deadlock kernel/locking/lockdep.c:1773 [inline]
 validate_chain kernel/locking/lockdep.c:2251 [inline]
 __lock_acquire+0xef2/0x3430 kernel/locking/lockdep.c:3340
 lock_acquire+0x2a1/0x630 kernel/locking/lockdep.c:3755
 lock_sock_nested+0xcb/0x120 net/core/sock.c:2536
 lock_sock include/net/sock.h:1460 [inline]
 sctp_close+0xcd/0x9d0 net/sctp/socket.c:1497
 inet_release+0xed/0x1c0 net/ipv4/af_inet.c:425
 inet6_release+0x50/0x70 net/ipv6/af_inet6.c:432
 sock_release+0x8d/0x1e0 net/socket.c:597
 __sock_create+0x38b/0x870 net/socket.c:1226
 sock_create+0x7f/0xa0 net/socket.c:1237
 sctp_do_peeloff+0x1a2/0x440 net/sctp/socket.c:4879
 sctp_getsockopt_peeloff net/sctp/socket.c:4914 [inline]
 sctp_getsockopt+0x111a/0x67e0 net/sctp/socket.c:6628
 sock_common_getsockopt+0x95/0xd0 net/core/sock.c:2690
 SYSC_getsockopt net/socket.c:1817 [inline]
 SyS_getsockopt+0x240/0x380 net/socket.c:1799
 entry_SYSCALL_64_fastpath+0x1f/0xc2

This warning is caused by the lock held by sctp_getsockopt() is on one
socket, while the other lock that sctp_close() is getting later is on
the newly created (which failed) socket during peeloff operation.

This patch is to avoid this warning by use lock_sock with subclass
SINGLE_DEPTH_NESTING as Wang Cong and Marcelo's suggestion.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Suggested-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Suggested-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 net/sctp/socket.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 8cdd6bbe2efa..172465b7c0f4 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1519,7 +1519,7 @@ static void sctp_close(struct sock *sk, long timeout)
=20
 	pr_debug("%s: sk:%p, timeout:%ld\n", __func__, sk, timeout);
=20
-	lock_sock(sk);
+	lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
 	sk->sk_shutdown =3D SHUTDOWN_MASK;
 	sk->sk_state =3D SCTP_SS_CLOSING;
=20
@@ -1569,7 +1569,7 @@ static void sctp_close(struct sock *sk, long timeout)
 	 * held and that should be grabbed before socket lock.
 	 */
 	spin_lock_bh(&net->sctp.addr_wq_lock);
-	bh_lock_sock(sk);
+	bh_lock_sock_nested(sk);
=20
 	/* Hold the sock, since sk_common_release() will put sock_put()
 	 * and we have just a little more cleanup.
--=20
2.15.1