Patchwork [1/2] tuntap: forbid calling TUNSETIFF when detached

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Submitter Jason Wang
Date Jan. 11, 2013, 8:50 a.m.
Message ID <1357894242-25020-1-git-send-email-jasowang@redhat.com>
Download mbox | patch
Permalink /patch/211245/
State Changes Requested
Delegated to: David Miller
Headers show

Comments

Jason Wang - Jan. 11, 2013, 8:50 a.m.
Michael points out that even after Stefan's fix the TUNSETIFF is still allowed
to create a new tap device. This because we only check tfile->tun but the
tfile->detached were introduced. Fix this by failing early in tun_set_iff() if
the file is detached. After this fix, there's no need to do the check again in
tun_set_iff(), so this patch removes it.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/net/tun.c |    5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)
Stefan Hajnoczi - Jan. 11, 2013, 2:42 p.m.
On Fri, Jan 11, 2013 at 04:50:41PM +0800, Jason Wang wrote:
> @@ -1546,6 +1544,9 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
>  	struct net_device *dev;
>  	int err;
>  
> +	if (rcu_dereference_protected(tfile->detached, lockdep_rtnl_is_held()))
> +		return -EINVAL;
> +

How come none of the other tfile->detached users call rcu_*()?

Stefan
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Eric Dumazet - Jan. 11, 2013, 2:55 p.m.
On Fri, 2013-01-11 at 16:50 +0800, Jason Wang wrote:

>  
> +	if (rcu_dereference_protected(tfile->detached, lockdep_rtnl_is_held()))
> +		return -EINVAL;
> +

Thats an open coded rtnl_dereference()

(please cleanup the whole tun.c file)



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Jason Wang - Jan. 12, 2013, 2:31 a.m.
On 01/11/2013 10:42 PM, Stefan Hajnoczi wrote:
> On Fri, Jan 11, 2013 at 04:50:41PM +0800, Jason Wang wrote:
>> @@ -1546,6 +1544,9 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
>>  	struct net_device *dev;
>>  	int err;
>>  
>> +	if (rcu_dereference_protected(tfile->detached, lockdep_rtnl_is_held()))
>> +		return -EINVAL;
>> +
> How come none of the other tfile->detached users call rcu_*()?

Right, no need to use rcu, the access were protected by rtnl lock.

Will repost.
> Stefan
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Jason Wang - Jan. 12, 2013, 2:31 a.m.
On 01/11/2013 10:55 PM, Eric Dumazet wrote:
> On Fri, 2013-01-11 at 16:50 +0800, Jason Wang wrote:
>
>>  
>> +	if (rcu_dereference_protected(tfile->detached, lockdep_rtnl_is_held()))
>> +		return -EINVAL;
>> +
> Thats an open coded rtnl_dereference()
>
> (please cleanup the whole tun.c file)
>

Sure.
>
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Patch

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 99b58d8..9a46d70 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -491,8 +491,6 @@  static int tun_attach(struct tun_struct *tun, struct file *file)
 	err = -EINVAL;
 	if (rcu_dereference_protected(tfile->tun, lockdep_rtnl_is_held()))
 		goto out;
-	if (tfile->detached && tun != tfile->detached)
-		goto out;
 
 	err = -EBUSY;
 	if (!(tun->flags & TUN_TAP_MQ) && tun->numqueues == 1)
@@ -1546,6 +1544,9 @@  static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 	struct net_device *dev;
 	int err;
 
+	if (rcu_dereference_protected(tfile->detached, lockdep_rtnl_is_held()))
+		return -EINVAL;
+
 	dev = __dev_get_by_name(net, ifr->ifr_name);
 	if (dev) {
 		if (ifr->ifr_flags & IFF_TUN_EXCL)