[PATCH net-next] net: em_canid: remove useless statements from em_canid_change

[PATCH net-next] net: em_canid: remove useless statements from em_canid_change

[Duan Jiong]

tcf_ematch is allocated by kzalloc in function tcf_em_tree_validate(),
so cm_old is always NULL.

Signed-off-by: Duan Jiong <duanj.fnst@cn.fujitsu.com>
---
 net/sched/em_canid.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/net/sched/em_canid.c b/net/sched/em_canid.c
index bfd34e4..7c292d4 100644
--- a/net/sched/em_canid.c
+++ b/net/sched/em_canid.c
@@ -125,7 +125,6 @@ static int em_canid_change(struct tcf_proto *tp, void *data, int len,
 {
 	struct can_filter *conf = data; /* Array with rules */
 	struct canid_match *cm;
-	struct canid_match *cm_old = (struct canid_match *)m->data;
 	int i;
 
 	if (!len)
@@ -181,12 +180,6 @@ static int em_canid_change(struct tcf_proto *tp, void *data, int len,
 
 	m->datalen = sizeof(struct canid_match) + len;
 	m->data = (unsigned long)cm;
-
-	if (cm_old != NULL) {
-		pr_err("canid: Configuring an existing ematch!\n");
-		kfree(cm_old);
-	}
-
 	return 0;
 }
 
-- 
1.8.3.1

Re: [PATCH net-next] net: em_canid: remove useless statements from em_canid_change

[David Miller]

From: Duan Jiong <duanj.fnst@cn.fujitsu.com>
Date: Wed, 18 Jun 2014 16:48:39 +0800

> tcf_ematch is allocated by kzalloc in function tcf_em_tree_validate(),
> so cm_old is always NULL.
> 
> Signed-off-by: Duan Jiong <duanj.fnst@cn.fujitsu.com>

Applied, thanks.

Re: [PATCH net-next] net: em_canid: remove useless statements from em_canid_change

[Oliver Hartkopp]

This is right for the first set of filters that is ever configured in
em_canid_change().

But what happens in an update case?
Does is turn the cm_old reference to a memory leak then?

Or do we always get a brand new "struct tcf_ematch *m" here??

Regards,
Oliver

On 22.06.2014 00:40, David Miller wrote:
> From: Duan Jiong <duanj.fnst@cn.fujitsu.com>
> Date: Wed, 18 Jun 2014 16:48:39 +0800
> 
>> tcf_ematch is allocated by kzalloc in function tcf_em_tree_validate(),
>> so cm_old is always NULL.
>>
>> Signed-off-by: Duan Jiong <duanj.fnst@cn.fujitsu.com>
> 
> Applied, thanks.
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Re: [PATCH net-next] net: em_canid: remove useless statements from em_canid_change

[David Miller]

From: Oliver Hartkopp <socketcan@hartkopp.net>
Date: Sun, 22 Jun 2014 18:27:34 +0200

> This is right for the first set of filters that is ever configured in
> em_canid_change().
> 
> But what happens in an update case?
> Does is turn the cm_old reference to a memory leak then?
> 
> Or do we always get a brand new "struct tcf_ematch *m" here??

There is only one call to this method is tcf_em_validate(), which also
unconditionally assigns new pointers to em->data without checking if
an existing non-NULL value is in em->data.  Specifically in the code
path where em->ops->change is not implemented.