net: devmem: preserve sockc_err

Preserve the error code returned by sock_cmsg_send and return that on
err.

Signed-off-by: Mina Almasry <almasrymina@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250523230524.1107879-4-almasrymina@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: mina

net/ipv4/tcp.c

@@ -1067,21 +1067,18 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
 	int flags, err, copied = 0;
 	int mss_now = 0, size_goal, copied_syn = 0;
 	int process_backlog = 0;
-	bool sockc_valid = true;
+	int sockc_err = 0;
 	int zc = 0;
 	long timeo;
 
 	flags = msg->msg_flags;
 
 	sockc = (struct sockcm_cookie){ .tsflags = READ_ONCE(sk->sk_tsflags) };
 	if (msg->msg_controllen) {
-		err = sock_cmsg_send(sk, msg, &sockc);
-		if (unlikely(err))
-			/* Don't return error until MSG_FASTOPEN has been
-			 * processed; that may succeed even if the cmsg is
-			 * invalid.
-			 */
-			sockc_valid = false;
+		sockc_err = sock_cmsg_send(sk, msg, &sockc);
+		/* Don't return error until MSG_FASTOPEN has been processed;
+		 * that may succeed even if the cmsg is invalid.
+		 */
 	}
 
 	if ((flags & MSG_ZEROCOPY) && size) {
@@ -1092,7 +1089,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
 		} else if (sock_flag(sk, SOCK_ZEROCOPY)) {
 			skb = tcp_write_queue_tail(sk);
 			uarg = msg_zerocopy_realloc(sk, size, skb_zcopy(skb),
-						    sockc_valid && !!sockc.dmabuf_id);
+						    !sockc_err && sockc.dmabuf_id);
 			if (!uarg) {
 				err = -ENOBUFS;
 				goto out_err;
@@ -1102,7 +1099,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
 			else
 				uarg_to_msgzc(uarg)->zerocopy = 0;
 
-			if (sockc_valid && sockc.dmabuf_id) {
+			if (!sockc_err && sockc.dmabuf_id) {
 				binding = net_devmem_get_binding(sk, sockc.dmabuf_id);
 				if (IS_ERR(binding)) {
 					err = PTR_ERR(binding);
@@ -1116,7 +1113,7 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
 			zc = MSG_SPLICE_PAGES;
 	}
 
-	if (sockc_valid && sockc.dmabuf_id &&
+	if (!sockc_err && sockc.dmabuf_id &&
 	    (!(flags & MSG_ZEROCOPY) || !sock_flag(sk, SOCK_ZEROCOPY))) {
 		err = -EINVAL;
 		goto out_err;
@@ -1160,9 +1157,8 @@ int tcp_sendmsg_locked(struct sock *sk, struct msghdr *msg, size_t size)
 		/* 'common' sending to sendq */
 	}
 
-	if (!sockc_valid) {
-		if (!err)
-			err = -EINVAL;
+	if (sockc_err) {
+		err = sockc_err;
 		goto out_err;
 	}