linux-kernel - [PATCH] net: remove release/lock_sock in tcp_splice

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Message-Id: <20240815084330.166987-1-sunyiqixm@gmail.com>
Date: Thu, 15 Aug 2024 16:43:30 +0800
From: sunyiqi <sunyiqixm@...il.com>
To: edumazet@...gle.com,
	davem@...emloft.net,
	dsahern@...nel.org,
	kuba@...nel.org,
	pabeni@...hat.com
Cc: netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	sunyiqi <sunyiqixm@...il.com>
Subject: [PATCH] net: remove release/lock_sock in tcp_splice_read

When enters tcp_splice_read, tcp_splice_read will call lock_sock
for sk in order to prevent other threads acquiring sk and release it
before return.

But in while(tss.len) loop, it releases and re-locks sk, give the other
thread a small window to lock the sk.

As a result, release/lock_sock in the while loop in tcp_splice_read may
cause race condition.

Fixes: 9c55e01c0cc8 ("[TCP]: Splice receive support.")
Signed-off-by: sunyiqi <sunyiqixm@...il.com>
---
 net/ipv4/tcp.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index e03a342c9162..7a2ce0e2e5be 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -856,8 +856,6 @@ ssize_t tcp_splice_read(struct socket *sock, loff_t *ppos,
 
 		if (!tss.len || !timeo)
 			break;
-		release_sock(sk);
-		lock_sock(sk);
 
 		if (sk->sk_err || sk->sk_state == TCP_CLOSE ||
 		    (sk->sk_shutdown & RCV_SHUTDOWN) ||
-- 
2.34.1