netdev - Re: [BUG] net_cls: Panic occured when net

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Date:	Sun, 31 May 2009 09:24:53 -0400
From:	jamal <hadi@...erus.ca>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	Minoru Usui <usui@....nes.nec.co.jp>, netdev@...r.kernel.org,
	containers@...ts.linux-foundation.org
Subject: Re: [BUG] net_cls: Panic occured when net_cls subsystem use

On Sun, 2009-05-31 at 10:12 +0200, Jarek Poplawski wrote:

> If somebody runs tc add filter with a new priority but existing handle
> a newly created (and not linked now) tc would be handled with goto
> errout and would leak, I guess.

This would imply the classifier is buggy. I will stare at the different
classifier - and if any exhibits such traits it needs to be fixed

> The change (in the two spots) is:
> > +               if (n->nlmsg_type == RTM_NEWTFILTER &&
> > +                   (n->nlmsg_flags&(NLM_F_CREATE|NLM_F_EXCL))) {
> > 
> 
> Sorry, but I don't think this change is enough; tc filter replace
> with only this (n->nlmsg_type == RTM_NEWTFILTER &&
> (n->nlmsg_flags&(NLM_F_CREATE))) can get here with an "old" tp
> and will relink it or destroy depending on the ->change() return.
> 

Excellent point - there could be buggy user space apps that will do
that. Minoru change the check to:

+               if (n->nlmsg_type == RTM_NEWTFILTER &&
+                   (n->nlmsg_flags&NLM_F_CREATE &&
+                    n->nlmsg_flags&NLM_F_EXCL)) {

cheers,
jamal

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