linux-kernel - [PATCH 5.4 45/56] net: udp: annotate data race around udp

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Date:   Mon,  4 Oct 2021 14:53:05 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 5.4 45/56] net: udp: annotate data race around udp_sk(sk)->corkflag

From: Eric Dumazet <edumazet@...gle.com>

commit a9f5970767d11eadc805d5283f202612c7ba1f59 upstream.

up->corkflag field can be read or written without any lock.
Annotate accesses to avoid possible syzbot/KCSAN reports.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv4/udp.c |   10 +++++-----
 net/ipv6/udp.c |    2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)

--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -981,7 +981,7 @@ int udp_sendmsg(struct sock *sk, struct
 	__be16 dport;
 	u8  tos;
 	int err, is_udplite = IS_UDPLITE(sk);
-	int corkreq = up->corkflag || msg->msg_flags&MSG_MORE;
+	int corkreq = READ_ONCE(up->corkflag) || msg->msg_flags&MSG_MORE;
 	int (*getfrag)(void *, char *, int, int, int, struct sk_buff *);
 	struct sk_buff *skb;
 	struct ip_options_data opt_copy;
@@ -1289,7 +1289,7 @@ int udp_sendpage(struct sock *sk, struct
 	}
 
 	up->len += size;
-	if (!(up->corkflag || (flags&MSG_MORE)))
+	if (!(READ_ONCE(up->corkflag) || (flags&MSG_MORE)))
 		ret = udp_push_pending_frames(sk);
 	if (!ret)
 		ret = size;
@@ -2551,9 +2551,9 @@ int udp_lib_setsockopt(struct sock *sk,
 	switch (optname) {
 	case UDP_CORK:
 		if (val != 0) {
-			up->corkflag = 1;
+			WRITE_ONCE(up->corkflag, 1);
 		} else {
-			up->corkflag = 0;
+			WRITE_ONCE(up->corkflag, 0);
 			lock_sock(sk);
 			push_pending_frames(sk);
 			release_sock(sk);
@@ -2676,7 +2676,7 @@ int udp_lib_getsockopt(struct sock *sk,
 
 	switch (optname) {
 	case UDP_CORK:
-		val = up->corkflag;
+		val = READ_ONCE(up->corkflag);
 		break;
 
 	case UDP_ENCAP:
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1231,7 +1231,7 @@ int udpv6_sendmsg(struct sock *sk, struc
 	int addr_len = msg->msg_namelen;
 	bool connected = false;
 	int ulen = len;
-	int corkreq = up->corkflag || msg->msg_flags&MSG_MORE;
+	int corkreq = READ_ONCE(up->corkflag) || msg->msg_flags&MSG_MORE;
 	int err;
 	int is_udplite = IS_UDPLITE(sk);
 	int (*getfrag)(void *, char *, int, int, int, struct sk_buff *);