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Date:   Fri, 13 May 2022 16:26:07 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        linux-kernel@...r.kernel.org,
        Pavel Begunkov <asml.silence@...il.com>
Subject: [PATCH net-next v3 02/10] udp/ipv6: move pending section of udpv6_sendmsg

Move up->pending section of udpv6_sendmsg() to the beginning of the
function. Even though it require some code duplication for sin6 parsing,
it clearly localises the pending handling in one place, removes an extra
if and more importantly will prepare the code for further patches.

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 net/ipv6/udp.c | 70 ++++++++++++++++++++++++++++++--------------------
 1 file changed, 42 insertions(+), 28 deletions(-)

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 11d44ed46953..85bff1252f5c 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1318,6 +1318,46 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	ipc6.sockc.tsflags = sk->sk_tsflags;
 	ipc6.sockc.mark = sk->sk_mark;
 
+	/* Rough check on arithmetic overflow,
+	   better check is made in ip6_append_data().
+	   */
+	if (unlikely(len > INT_MAX - sizeof(struct udphdr)))
+		return -EMSGSIZE;
+
+	getfrag  =  is_udplite ?  udplite_getfrag : ip_generic_getfrag;
+
+	/* There are pending frames. */
+	if (up->pending) {
+		if (up->pending == AF_INET)
+			return udp_sendmsg(sk, msg, len);
+
+		/* Do a quick destination sanity check before corking. */
+		if (sin6) {
+			if (msg->msg_namelen < offsetof(struct sockaddr, sa_data))
+				return -EINVAL;
+			if (sin6->sin6_family == AF_INET6) {
+				if (msg->msg_namelen < SIN6_LEN_RFC2133)
+					return -EINVAL;
+				if (ipv6_addr_any(&sin6->sin6_addr) &&
+				    ipv6_addr_v4mapped(&np->saddr))
+					return -EINVAL;
+			} else if (sin6->sin6_family != AF_UNSPEC) {
+				return -EINVAL;
+			}
+		}
+
+		/* The socket lock must be held while it's corked. */
+		lock_sock(sk);
+		if (unlikely(up->pending != AF_INET6)) {
+			/* Just now it was seen corked, userspace is buggy */
+			err = up->pending ? -EAFNOSUPPORT : -EINVAL;
+			release_sock(sk);
+			return err;
+		}
+		dst = NULL;
+		goto do_append_data;
+	}
+
 	/* destination address check */
 	if (sin6) {
 		if (addr_len < offsetof(struct sockaddr, sa_data))
@@ -1343,12 +1383,11 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		default:
 			return -EINVAL;
 		}
-	} else if (!up->pending) {
+	} else {
 		if (sk->sk_state != TCP_ESTABLISHED)
 			return -EDESTADDRREQ;
 		daddr = &sk->sk_v6_daddr;
-	} else
-		daddr = NULL;
+	}
 
 	if (daddr) {
 		if (ipv6_addr_v4mapped(daddr)) {
@@ -1365,31 +1404,6 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		}
 	}
 
-	/* Rough check on arithmetic overflow,
-	   better check is made in ip6_append_data().
-	   */
-	if (len > INT_MAX - sizeof(struct udphdr))
-		return -EMSGSIZE;
-
-	getfrag  =  is_udplite ?  udplite_getfrag : ip_generic_getfrag;
-	if (up->pending) {
-		if (up->pending == AF_INET)
-			return udp_sendmsg(sk, msg, len);
-		/*
-		 * There are pending frames.
-		 * The socket lock must be held while it's corked.
-		 */
-		lock_sock(sk);
-		if (likely(up->pending)) {
-			if (unlikely(up->pending != AF_INET6)) {
-				release_sock(sk);
-				return -EAFNOSUPPORT;
-			}
-			dst = NULL;
-			goto do_append_data;
-		}
-		release_sock(sk);
-	}
 	ulen += sizeof(struct udphdr);
 
 	memset(fl6, 0, sizeof(*fl6));
-- 
2.36.0

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