[PATCH net] net: sched: fix unbalance in the error path of tca_action_flush()

[PATCH net] net: sched: fix unbalance in the error path of tca_action_flush()

[Davide Caratti]

When tca_action_flush() calls the action walk() and gets an error,
a successful call to nla_nest_start() is not followed by a call to
nla_nest_cancel(). It's harmless, as the skb is freed in the error
path - but it's worth to fix this unbalance.

Signed-off-by: Davide Caratti <dcaratti@redhat.com>
---
 net/sched/act_api.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/sched/act_api.c b/net/sched/act_api.c
index eba6682727dd..43f4991b7777 100644
--- a/net/sched/act_api.c
+++ b/net/sched/act_api.c
@@ -938,8 +938,10 @@ static int tca_action_flush(struct net *net, struct nlattr *nla,
 		goto out_module_put;
 
 	err = ops->walk(net, skb, &dcb, RTM_DELACTION, ops);
-	if (err <= 0)
+	if (err <= 0) {
+		nla_nest_cancel(skb, nest);
 		goto out_module_put;
+	}
 
 	nla_nest_end(skb, nest);
 
-- 
2.14.3

Re: [PATCH net] net: sched: fix unbalance in the error path of tca_action_flush()

[Jamal Hadi Salim]

On 18-02-15 09:50 AM, Davide Caratti wrote:
> When tca_action_flush() calls the action walk() and gets an error,
> a successful call to nla_nest_start() is not followed by a call to
> nla_nest_cancel(). It's harmless, as the skb is freed in the error
> path - but it's worth to fix this unbalance.

Kind of pushing the boundaries saying this targets net tree - there is
no bug you are fixing (as you say the sk is freed).
Maybe it makes the code prettier ...

cheers,
jamal

Re: [PATCH net] net: sched: fix unbalance in the error path of tca_action_flush()

[Davide Caratti]

On Thu, 2018-02-15 at 10:31 -0500, Jamal Hadi Salim wrote:
> On 18-02-15 09:50 AM, Davide Caratti wrote:
> > When tca_action_flush() calls the action walk() and gets an error,
> > a successful call to nla_nest_start() is not followed by a call to
> > nla_nest_cancel(). It's harmless, as the skb is freed in the error
> > path - but it's worth to fix this unbalance.
> 
> Kind of pushing the boundaries saying this targets net tree - there is
> no bug you are fixing (as you say the sk is freed).
> Maybe it makes the code prettier ...

you are right, this fix is only cosmetic as long as the skb is no more
used after walk() returns an error. It just triggered the doubt to me
while I was reading the series that added support to ext_acks, and this is
the followup.

David, please apply to net-next (or drop it, at your convenience).

thank you in advance,
-- 
davide

Re: [PATCH net] net: sched: fix unbalance in the error path of tca_action_flush()

[David Miller]

From: Davide Caratti <dcaratti@redhat.com>
Date: Thu, 15 Feb 2018 15:50:57 +0100

> When tca_action_flush() calls the action walk() and gets an error,
> a successful call to nla_nest_start() is not followed by a call to
> nla_nest_cancel(). It's harmless, as the skb is freed in the error
> path - but it's worth to fix this unbalance.
> 
> Signed-off-by: Davide Caratti <dcaratti@redhat.com>

Applied to net-next, thanks.