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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Stefan Raspl <raspl@linux.ibm.com>,
        "David S. Miller" <davem@davemloft.net>,
        Sasha Levin <alexander.levin@microsoft.com>,
        Ursula Braun <ubraun@linux.ibm.com>
Subject: [PATCH 4.16 172/279] smc: fix sendpage() call
Date:   Mon, 18 Jun 2018 10:12:37 +0200
Message-Id: <20180618080615.935334248@linuxfoundation.org>
In-Reply-To: <20180618080608.851973560@linuxfoundation.org>
References: <20180618080608.851973560@linuxfoundation.org>
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4.16-stable review patch.  If anyone has any objections, please let me know.

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

From: Stefan Raspl <stefan.raspl@linux.ibm.com>

[ Upstream commit bda27ff5c4526f80a7620a94ecfe8dca153e3696 ]

The sendpage() call grabs the sock lock before calling the default
implementation - which tries to grab it once again.

Signed-off-by: Stefan Raspl <raspl@linux.ibm.com>
Signed-off-by: Ursula Braun <ubraun@linux.ibm.com><
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/smc/af_smc.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -1313,8 +1313,11 @@ static ssize_t smc_sendpage(struct socke
 
 	smc = smc_sk(sk);
 	lock_sock(sk);
-	if (sk->sk_state != SMC_ACTIVE)
+	if (sk->sk_state != SMC_ACTIVE) {
+		release_sock(sk);
 		goto out;
+	}
+	release_sock(sk);
 	if (smc->use_fallback)
 		rc = kernel_sendpage(smc->clcsock, page, offset,
 				     size, flags);
@@ -1322,7 +1325,6 @@ static ssize_t smc_sendpage(struct socke
 		rc = sock_no_sendpage(sock, page, offset, size, flags);
 
 out:
-	release_sock(sk);
 	return rc;
 }