[PATCH v2 1/2] net: sctp: socket: Fix uninitialized error on socket shutdown

[luoqing <l1138897701@163.com>]

From: luoqing <luoqing@kylinos.cn>

When sctp_skb_recv_datagram() detects sk->sk_shutdown & RCV_SHUTDOWN,
it breaks out of the loop and returns NULL without setting *err.
This leaves the error pointer uninitialized or with a stale value,
which can confuse callers expecting a clean shutdown indication.

Compare with the generic __skb_wait_for_more_packets() in
net/core/datagram.c which properly handles shutdown by setting *err = 0.

Fix this by setting *err = 0 before breaking when the socket is shut down,
indicating an orderly shutdown rather than an error condition.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")

Signed-off-by: luoqing <luoqing@kylinos.cn>
---
 net/sctp/socket.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/sctp/socket.c b/net/sctp/socket.c
index c7b9e325ec1c..ea7050b27715 100644
--- a/net/sctp/socket.c
+++ b/net/sctp/socket.c
@@ -9117,8 +9117,10 @@ struct sk_buff *sctp_skb_recv_datagram(struct sock *sk, int flags, int *err)
 		if (error)
 			goto no_packet;
 
-		if (sk->sk_shutdown & RCV_SHUTDOWN)
+		if (sk->sk_shutdown & RCV_SHUTDOWN) {
+			*err = 0;
 			break;
+		}
 
 
 		/* User doesn't want to wait.  */
-- 
2.25.1