netdev - [PATCH net] net: udp: annotate data race around udp

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Message-Id: <20210928002924.629469-1-eric.dumazet@gmail.com>
Date:   Mon, 27 Sep 2021 17:29:24 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net] net: udp: annotate data race around udp_sk(sk)->corkflag

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

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>
---
 net/ipv4/udp.c | 10 +++++-----
 net/ipv6/udp.c |  2 +-
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 8851c9463b4b62c9017565f545250c4ffe22927c..2a7825a5b84254b70b2f06fc04d601719c2e0bc3 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -1053,7 +1053,7 @@ int udp_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	__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;
@@ -1361,7 +1361,7 @@ int udp_sendpage(struct sock *sk, struct page *page, int offset,
 	}
 
 	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;
@@ -2662,9 +2662,9 @@ int udp_lib_setsockopt(struct sock *sk, int level, int optname,
 	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);
@@ -2787,7 +2787,7 @@ int udp_lib_getsockopt(struct sock *sk, int level, int optname,
 
 	switch (optname) {
 	case UDP_CORK:
-		val = up->corkflag;
+		val = READ_ONCE(up->corkflag);
 		break;
 
 	case UDP_ENCAP:
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index ea53847b5b7e8b82f1898fa442327a9ce060085f..e505bb007e9f97995bf64a37702e0dc44a8c4a5c 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1303,7 +1303,7 @@ int udpv6_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 	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 *);
-- 
2.33.0.685.g46640cef36-goog