[PATCH net] sctp: fix race between sctp_wait_for_connect and peeloff

[Zhenghang Xiao <kipreyyy@gmail.com>]

sctp_wait_for_connect() drops and re-acquires the socket lock while
waiting for the association to reach ESTABLISHED state. During this
window, another thread can peeloff the association to a new socket via
getsockopt(SCTP_SOCKOPT_PEELOFF), changing asoc->base.sk. After
re-acquiring the old socket lock, sctp_wait_for_connect() returns
success without noticing the migration — the caller then accesses
the association under the wrong lock in sctp_datamsg_from_user().

Add the same sk != asoc->base.sk check that sctp_wait_for_sndbuf()
already has, returning an error if the association was migrated while
we slept.

Fixes: 668c9beb9020 ("sctp: implement assign_number for sctp_stream_interleave")
Signed-off-by: Zhenghang Xiao <kipreyyy@gmail.com>
---
 net/sctp/socket.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index 1d2568bb6bc2..66e12fb0c646 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -9403,6 +9403,8 @@ static int sctp_wait_for_connect(struct sctp_association *asoc, long *timeo_p)
 		release_sock(sk);
 		current_timeo = schedule_timeout(current_timeo);
 		lock_sock(sk);
+		if (sk != asoc->base.sk)
+			goto do_error;
 
 		*timeo_p = current_timeo;
 	}
-- 
2.50.1 (Apple Git-155)