netdev - [PATCH v1 net 10/15] af_unix: Annotate data-races around sk->sk

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Date: Mon, 3 Jun 2024 07:32:26 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
	<edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni
	<pabeni@...hat.com>
CC: Kuniyuki Iwashima <kuniyu@...zon.com>, Kuniyuki Iwashima
	<kuni1840@...il.com>, <netdev@...r.kernel.org>
Subject: [PATCH v1 net 10/15] af_unix: Annotate data-races around sk->sk_sndbuf.

sk_setsockopt() changes sk->sk_sndbuf under lock_sock(), but it's
not used in af_unix.c.

Let's use READ_ONCE() to read sk->sk_sndbuf in unix_writable(),
unix_dgram_sendmsg(), and unix_stream_sendmsg().

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
 net/unix/af_unix.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 8eadc6464301..e99b94fc80b3 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -533,7 +533,7 @@ static int unix_dgram_peer_wake_me(struct sock *sk, struct sock *other)
 static int unix_writable(const struct sock *sk, unsigned char state)
 {
 	return state != TCP_LISTEN &&
-	       (refcount_read(&sk->sk_wmem_alloc) << 2) <= sk->sk_sndbuf;
+		(refcount_read(&sk->sk_wmem_alloc) << 2) <= READ_ONCE(sk->sk_sndbuf);
 }
 
 static void unix_write_space(struct sock *sk)
@@ -1967,7 +1967,7 @@ static int unix_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
 	}
 
 	err = -EMSGSIZE;
-	if (len > sk->sk_sndbuf - 32)
+	if (len > READ_ONCE(sk->sk_sndbuf) - 32)
 		goto out;
 
 	if (len > SKB_MAX_ALLOC) {
@@ -2247,7 +2247,7 @@ static int unix_stream_sendmsg(struct socket *sock, struct msghdr *msg,
 						   &err, 0);
 		} else {
 			/* Keep two messages in the pipe so it schedules better */
-			size = min_t(int, size, (sk->sk_sndbuf >> 1) - 64);
+			size = min_t(int, size, (READ_ONCE(sk->sk_sndbuf) >> 1) - 64);
 
 			/* allow fallback to order-0 allocations */
 			size = min_t(int, size, SKB_MAX_HEAD(0) + UNIX_SKB_FRAGS_SZ);
-- 
2.30.2