linux-kernel - [PATCH 3.18 18/54] ip_tunnel: Fix name string concatenate in __ip_tunnel

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Date:   Tue, 11 Dec 2018 16:41:06 +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, Sultan Alsawaf <sultanxda@...il.com>,
        "David S. Miller" <davem@...emloft.net>
Subject: [PATCH 3.18 18/54] ip_tunnel: Fix name string concatenate in __ip_tunnel_create()

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

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

From: Sultan Alsawaf <sultanxda@...il.com>

commit 000ade8016400d93b4d7c89970d96b8c14773d45 upstream.

By passing a limit of 2 bytes to strncat, strncat is limited to writing
fewer bytes than what it's supposed to append to the name here.

Since the bounds are checked on the line above this, just remove the string
bounds checks entirely since they're unneeded.

Signed-off-by: Sultan Alsawaf <sultanxda@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 net/ipv4/ip_tunnel.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -310,8 +310,8 @@ static struct net_device *__ip_tunnel_cr
 	} else {
 		if (strlen(ops->kind) > (IFNAMSIZ - 3))
 			goto failed;
-		strlcpy(name, ops->kind, IFNAMSIZ);
-		strncat(name, "%d", 2);
+		strcpy(name, ops->kind);
+		strcat(name, "%d");
 	}

 	ASSERT_RTNL();