linux-kernel - [PATCH 5.3 07/48] net/smc: fix fastopen for non-blocking connect()

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Message-Id: <20191119050953.406107089@linuxfoundation.org>
Date:   Tue, 19 Nov 2019 06:19:27 +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,
        syzbot+8488cc4cf1c9e09b8b86@...kaller.appspotmail.com,
        Ursula Braun <ubraun@...ux.ibm.com>,
        Karsten Graul <kgraul@...ux.ibm.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 5.3 07/48] net/smc: fix fastopen for non-blocking connect()

From: Ursula Braun <ubraun@...ux.ibm.com>

[ Upstream commit 8204df72bea1a7d83d0777add6da98a41dfbdc34 ]

FASTOPEN does not work with SMC-sockets. Since SMC allows fallback to
TCP native during connection start, the FASTOPEN setsockopts trigger
this fallback, if the SMC-socket is still in state SMC_INIT.
But if a FASTOPEN setsockopt is called after a non-blocking connect(),
this is broken, and fallback does not make sense.
This change complements
commit cd2063604ea6 ("net/smc: avoid fallback in case of non-blocking connect")
and fixes the syzbot reported problem "WARNING in smc_unhash_sk".

Reported-by: syzbot+8488cc4cf1c9e09b8b86@...kaller.appspotmail.com
Fixes: e1bbdd570474 ("net/smc: reduce sock_put() for fallback sockets")
Signed-off-by: Ursula Braun <ubraun@...ux.ibm.com>
Signed-off-by: Karsten Graul <kgraul@...ux.ibm.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/smc/af_smc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1731,7 +1731,7 @@ static int smc_setsockopt(struct socket
 	case TCP_FASTOPEN_KEY:
 	case TCP_FASTOPEN_NO_COOKIE:
 		/* option not supported by SMC */
-		if (sk->sk_state == SMC_INIT) {
+		if (sk->sk_state == SMC_INIT && !smc->connect_nonblock) {
 			smc_switch_to_fallback(smc);
 			smc->fallback_rsn = SMC_CLC_DECL_OPTUNSUPP;
 		} else {