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Subject[PATCH AUTOSEL for 4.4 013/162] sctp: fix recursive locking warning in sctp_do_peeloff
From: Xin Long <>

[ 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

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 <>
Suggested-by: Marcelo Ricardo Leitner <>
Suggested-by: Cong Wang <>
Signed-off-by: Xin Long <>
Acked-by: Marcelo Ricardo Leitner <>
Signed-off-by: David S. Miller <>
Signed-off-by: Sasha Levin <>
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 df6a4b2d0728..8efdf7fc1044 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -1518,7 +1518,7 @@ static void sctp_close(struct sock *sk, long timeout)

pr_debug("%s: sk:%p, timeout:%ld\n", __func__, sk, timeout);

- lock_sock(sk);
+ lock_sock_nested(sk, SINGLE_DEPTH_NESTING);
sk->sk_shutdown = SHUTDOWN_MASK;
sk->sk_state = SCTP_SS_CLOSING;

@@ -1569,7 +1569,7 @@ static void sctp_close(struct sock *sk, long timeout)
* held and that should be grabbed before socket lock.
- bh_lock_sock(sk);
+ bh_lock_sock_nested(sk);

/* Hold the sock, since sk_common_release() will put sock_put()
* and we have just a little more cleanup.
 \ /
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