linux-kernel - Re: [PATCH 1/7] netfilter: ipset: refactor deprecated strncpy

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Message-ID: <202308081659.BD539443@keescook>
Date:   Tue, 8 Aug 2023 17:00:11 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Florian Westphal <fw@...len.de>
Cc:     Justin Stitt <justinstitt@...gle.com>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        linux-hardening@...r.kernel.org, netfilter-devel@...r.kernel.org,
        coreteam@...filter.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/7] netfilter: ipset: refactor deprecated strncpy

On Wed, Aug 09, 2023 at 01:38:55AM +0200, Florian Westphal wrote:
> Justin Stitt <justinstitt@...gle.com> wrote:
> > Fixes several buffer overread bugs present in `ip_set_core.c` by using
> > `strscpy` over `strncpy`.
> > 
> > Link: https://github.com/KSPP/linux/issues/90
> > Cc: linux-hardening@...r.kernel.org
> > Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> > 
> > ---
> > There exists several potential buffer overread bugs here. These bugs
> > exist due to the fact that the destination and source strings may have
> > the same length which is equal to the max length `IPSET_MAXNAMELEN`.
> 
> There is no truncation.  Inputs are checked via nla_policy:
> 
> [IPSET_ATTR_SETNAME2]   = { .type = NLA_NUL_STRING, .len = IPSET_MAXNAMELEN - 1 },

Ah, perfect. Yeah, so if it needs to zero-padding, but it is always
NUL-terminated, strscpy_pad() is the right replacement. Thanks!

-- 
Kees Cook