[net] net: fix sysfs symlinks of adjacent devices

From: "Alexander Y. Fomichev" <git.user@gmail.com>

__netdev_adjacent_dev_insert may add adjacent device from another
namespace. Without proper check it leads to emergence of broken
symlink from/to device not existing in current namespace.
Fix: check net_ns is the same before netdev_adjacent_sysfs_add/del
related to: 4c75431ac3520631f1d9e74aa88407e6374dbbc4

Signed-off-by: Alexander Y. Fomichev <git.user@gmail.com>
---
 net/core/dev.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

On 09/12/2014 06:13 AM, Alexander Fomichev wrote:
> From: "Alexander Y. Fomichev" <git.user@gmail.com>
> 
> __netdev_adjacent_dev_insert may add adjacent device from another
> namespace. Without proper check it leads to emergence of broken
> symlink from/to device not existing in current namespace.
> Fix: check net_ns is the same before netdev_adjacent_sysfs_add/del
> related to: 4c75431ac3520631f1d9e74aa88407e6374dbbc4
> 
> Signed-off-by: Alexander Y. Fomichev <git.user@gmail.com>
> ---
>  net/core/dev.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/net/core/dev.c b/net/core/dev.c
> index ab9a16530c36..887784b2dcde 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -4841,7 +4841,8 @@ static int __netdev_adjacent_dev_insert(struct net_device *dev,
>  	pr_debug("dev_hold for %s, because of link added from %s to %s\n",
>  		 adj_dev->name, dev->name, adj_dev->name);
>  
> -	if (netdev_adjacent_is_neigh_list(dev, dev_list)) {
> +	if (netdev_adjacent_is_neigh_list(dev, dev_list) &&
> +	    net_eq(dev_net(dev), dev_net(adj_dev))) {
>  		ret = netdev_adjacent_sysfs_add(dev, adj_dev, dev_list);
>  		if (ret)
>  			goto free_adj;
> @@ -4862,7 +4863,8 @@ static int __netdev_adjacent_dev_insert(struct net_device *dev,
>  	return 0;
>  
>  remove_symlinks:
> -	if (netdev_adjacent_is_neigh_list(dev, dev_list))
> +	if (netdev_adjacent_is_neigh_list(dev, dev_list) &&
> +	    net_eq(dev_net(dev), dev_net(adj_dev)))
>  		netdev_adjacent_sysfs_del(dev, adj_dev->name, dev_list);
>  free_adj:
>  	kfree(adj);
> 

Looking over the code, it might make sense to move all the net_eq checks
into adjacent_sysfs calls so as to consolidate them.  I haven't audited
all code paths, but at first glance it should do the right thing.

What do you think?

-vlad
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Hi,

On 2014-09-12 14:13:46 +0400, Alexander Fomichev wrote:
> From: "Alexander Y. Fomichev" <git.user@gmail.com>
> 
> __netdev_adjacent_dev_insert may add adjacent device from another
> namespace. Without proper check it leads to emergence of broken
> symlink from/to device not existing in current namespace.
> Fix: check net_ns is the same before netdev_adjacent_sysfs_add/del
> related to: 4c75431ac3520631f1d9e74aa88407e6374dbbc4
> 

This version, applied on top of 8ba4caf1ee, fixes the bug I had
reported. Not just the testcase, but the actual usage scenario.

I haven't tested David's version, but it doesn't look likely to be
materially different.

Greetings,

Andres Freund
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html