Date:   Thu, 9 Feb 2023 21:17:12 +0100
From:   Florian Westphal <fw@strlen.de>
To:     Jan Engelhardt <jengelh@inai.de>
Cc:     Florian Westphal <fw@strlen.de>,
        Igor Artemiev <Igor.A.Artemiev@mcst.ru>,
        Pablo Neira Ayuso <pablo@netfilter.org>,
        Jozsef Kadlecsik <kadlec@netfilter.org>,
        netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
        netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
        lvc-project@linuxtesting.org
Subject: Re: [lvc-project] [PATCH] netfilter: xt_recent: Fix attempt to
 update removed entry
Message-ID: <20230209201712.GB17303@breakpoint.cc>
References: <20230209125831.2674811-1-Igor.A.Artemiev@mcst.ru>
 <20230209150733.GA17303@breakpoint.cc>
 <6152n4q7-1ssr-521p-786s-71q4q9731370@vanv.qr>
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Jan Engelhardt <jengelh@inai.de> wrote:
> On Thursday 2023-02-09 16:07, Florian Westphal wrote:
> 
> >Igor Artemiev <Igor.A.Artemiev@mcst.ru> wrote:
> >> When both --remove and --update flag are specified, there's a code
> >> path at which the entry to be updated is removed beforehand,
> >> that leads to kernel crash. Update entry, if --remove flag
> >> don't specified.
> >> 
> >> Found by Linux Verification Center (linuxtesting.org) with SVACE.
> >
> >How did you manage to do this?  --update and --remove are supposed
> >to be mutually exclusive.
> 
> I suppose the exclusivity is only checked at the iptables command-line
> and neverwhere else.

Removing the userspace check gives me an -EINVAL from checkentry.