linux-kernel - [PATCH 4.9 074/109] tcp: correct memory barrier usage in tcp_check

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Date:   Thu,  7 Dec 2017 13:56:58 +0100
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 <eric.dumazet@...il.com>,
        Oleg Nesterov <oleg@...hat.com>,
        Jason Baron <jbaron@...mai.com>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.9 074/109] tcp: correct memory barrier usage in tcp_check_space()

4.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Jason Baron <jbaron@...mai.com>


[ Upstream commit 56d806222ace4c3aeae516cd7a855340fb2839d8 ]

sock_reset_flag() maps to __clear_bit() not the atomic version clear_bit().
Thus, we need smp_mb(), smp_mb__after_atomic() is not sufficient.

Fixes: 3c7151275c0c ("tcp: add memory barriers to write space paths")
Cc: Eric Dumazet <eric.dumazet@...il.com>
Cc: Oleg Nesterov <oleg@...hat.com>
Signed-off-by: Jason Baron <jbaron@...mai.com>
Acked-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: Oleg Nesterov <oleg@...hat.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv4/tcp_input.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5081,7 +5081,7 @@ static void tcp_check_space(struct sock
 	if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) {
 		sock_reset_flag(sk, SOCK_QUEUE_SHRUNK);
 		/* pairs with tcp_poll() */
-		smp_mb__after_atomic();
+		smp_mb();
 		if (sk->sk_socket &&
 		    test_bit(SOCK_NOSPACE, &sk->sk_socket->flags))
 			tcp_new_space(sk);