tun: allow positive return values on dev_get_valid_name() call

BugLink: https://launchpad.net/bugs/1748846
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>
(cherry picked from commit 5c25f65fd1e42685f7ccd80e0621829c105785d9)
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Acked-by: Brad Figg <brad.figg@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 9e7b4e7d3f974b2d47e4b53822b82e3b304f0eb9..87d18f313ebc7495af77b0cb362a952908357ed4 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1814,7 +1814,7 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
                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);