From: Alban Browaeys <alban.browaeys@gmail.com>
To: Pablo Neira Ayuso <pablo@netfilter.org>
Cc: Patrick McHardy <kaber@trash.net>,
Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>,
"David S. Miller" <davem@davemloft.net>,
netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] netfilter: xt_hashlimit: Fix integer divide round to zero.
Date: Mon, 06 Feb 2017 15:28:07 +0100 [thread overview]
Message-ID: <1486391287.2374.1.camel@gmail.com> (raw)
In-Reply-To: <20170206130443.GA10990@salvia>
Le lundi 06 février 2017 à 14:04 +0100, Pablo Neira Ayuso a écrit :
> On Sat, Feb 04, 2017 at 11:47:31PM +0100, Alban Browaeys wrote:
> > diff --git a/net/netfilter/xt_hashlimit.c
> > b/net/netfilter/xt_hashlimit.c
> > index 10063408141d..df75ad643eef 100644
> > --- a/net/netfilter/xt_hashlimit.c
> > +++ b/net/netfilter/xt_hashlimit.c
> > @@ -463,21 +463,19 @@ static u32 xt_hashlimit_len_to_chunks(u32 len)
> > /* Precision saver. */
> > static u64 user2credits(u64 user, int revision)
> > {
> > > > + /* Avoid overflow: divide the constant operands first */
> > > > if (revision == 1) {
> > > > - /* If multiplying would overflow... */
> > > > - if (user > 0xFFFFFFFF / (HZ*CREDITS_PER_JIFFY_v1))
> > > > - /* Divide first. */
> > > > - return div64_u64(user, XT_HASHLIMIT_SCALE)
> > > > - * HZ * CREDITS_PER_JIFFY_v1;
> > > > + return div64_u64(user, div64_u64(XT_HASHLIMIT_SCALE,
> > > > + HZ * CREDITS_PER_JIFFY_v1));
> >
> > > > - return div64_u64(user * HZ * CREDITS_PER_JIFFY_v1,
> > > > + return user * div64_u64(HZ * CREDITS_PER_JIFFY_v1,
> > XT_HASHLIMIT_SCALE);
>
> I see two return statements here, the one coming later is
> shadowed, this can't be right.
I fixed revision 2 case then copy the code to revision 1
and lost the condition in the process.
The code duplication is useless. I will rework it in v2.
Thank you for the review.
next prev parent reply other threads:[~2017-02-06 14:28 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-04 22:47 [PATCH] netfilter: xt_hashlimit: Fix integer divide round to zero Alban Browaeys
2017-02-06 13:04 ` Pablo Neira Ayuso
2017-02-06 14:28 ` Alban Browaeys [this message]
2017-02-06 22:50 ` [PATCH v2] " Alban Browaeys
2017-02-21 12:48 ` Pablo Neira Ayuso
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