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    SubjectRe: [Stable-review] [104/145] netfilter: xt_recent: fix false match
    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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