Messages in this thread | | | Date | Sat, 13 Mar 2010 18:01:31 +0100 | From | Willy Tarreau <> | Subject | Re: [Stable-review] [104/145] netfilter: xt_recent: fix false match |
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On Sat, Mar 13, 2010 at 07:40:03AM -0700, Tim Gardner wrote: > On 03/12/2010 11:24 PM, Willy Tarreau wrote: > >On Fri, Mar 12, 2010 at 04:27:17PM -0800, Greg KH wrote: > >>2.6.32-stable review patch. If anyone has any objections, please let me > >>know. > >> > >>---------------- > >>From: Tim Gardner<tim.gardner@canonical.com> > >> > >>commit 8ccb92ad41cb311e52ad1b1fe77992c7f47a3b63 upstream. > >> > >>A rule with a zero hit_count will always match. > >> > >>Signed-off-by: Tim Gardner<tim.gardner@canonical.com> > >>Signed-off-by: Patrick McHardy<kaber@trash.net> > >>Signed-off-by: Greg Kroah-Hartman<gregkh@suse.de> > >> > >>--- > >> net/netfilter/xt_recent.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >>--- a/net/netfilter/xt_recent.c > >>+++ b/net/netfilter/xt_recent.c > >>@@ -260,7 +260,7 @@ recent_mt(const struct sk_buff *skb, con > >> for (i = 0; i< e->nstamps; i++) { > >> if (info->seconds&& time_after(time, e->stamps[i])) > >> continue; > >>- if (++hits>= info->hit_count) { > >>+ if (info->hit_count&& ++hits>= info->hit_count) { > >> ret = !ret; > >> break; > >> } > > > >I don't know if this has any undesired side effect or not, but the > >logic is changed now since "hits" will not be increased anymore when > >info->hit_count is zero. And the code does not make it obvious to me > >what the intended purpose was. > > > >For this reason I always find it dangerous to change variables in > >if() conditions because it's where we change operations the most > >frequently when fixing bugs. > > > >Willy > > > > Willy - I agree with you that changing variables in an if() clause can > be dangerous. I did consider the possibility for side effects in this > case, but decided to go with the simplest patch since 'hits' is local to > the scope of the the surrounding else if() clause and is used in no > other place.
indeed, but before the patch, "hits" was increased at every pass in the loop. Now it's only increased for passes which have a non-zero hit_count, so in theory it can change the result of the test for further passes of the loop. I just don't know if it can have any effect, but I trust you since you had to understand the code for the change :-)
Regards, Willy
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