[PATCH net] tun: allow positive return values on dev_get_valid_name() call

[PATCH net] tun: allow positive return values on dev_get_valid_name() call

[Julien Gomes]

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>
---
 drivers/net/tun.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index ea29da91ea5a..4d2400c253ba 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -2253,7 +2253,7 @@ 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);
-- 
2.14.2

Re: [PATCH net] tun: allow positive return values on dev_get_valid_name() call

[Cong Wang]

On Wed, Oct 25, 2017 at 11:50 AM, Julien Gomes <julien@arista.com> wrote:
> 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>

Good catch! I missed this case indeed. We'd better document it
in the future.

Acked-by: Cong Wang <xiyou.wangcong@gmail.com>

Re: [PATCH net] tun: allow positive return values on dev_get_valid_name() call

[David Miller]

From: Julien Gomes <julien@arista.com>
Date: Wed, 25 Oct 2017 11:50:50 -0700

> 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>

Applied, thanks.

Re: [PATCH net] tun: allow positive return values on dev_get_valid_name() call

[David Miller]

From: Julien Gomes <julien@arista.com>
Date: Wed, 25 Oct 2017 11:50:50 -0700

> 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>

Applied.