From: Julien Gomes <julien@arista.com>
Date: Wed, 25 Oct 2017 11:50:50 -0700
Subject: tun: allow positive return values on dev_get_valid_name() call
Git-commit: 5c25f65fd1e42685f7ccd80e0621829c105785d9
Patch-mainline: v4.14-rc7
References: networking-stable-17_11_14, CVE-2018-7191, bsc#1135603

If the name argument of dev_get_valid_name() contains "%d", it will try
to assign it a unit number in __dev__alloc_name() and return either the
unit number (>= 0) or an error code (< 0).
Considering positive values as error values prevent tun device creations
relying this mechanism, therefor we should only consider negative values
as errors here.

Signed-off-by: Julien Gomes <julien@arista.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/net/tun.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1811,7 +1811,7 @@ static int tun_set_iff(struct net *net,
 		if (!dev)
 			return -ENOMEM;
 		err = dev_get_valid_name(net, dev, name);
-		if (err)
+		if (err < 0)
 			goto err_free_dev;
 
 		dev_net_set(dev, net);