linux-kernel - Re: [lvc-project] [PATCH] netfilter: xt_recent: Fix attempt to update removed entry

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Date:   Thu, 9 Feb 2023 21:17:12 +0100
From:   Florian Westphal <fw@...len.de>
To:     Jan Engelhardt <jengelh@...i.de>
Cc:     Florian Westphal <fw@...len.de>,
        Igor Artemiev <Igor.A.Artemiev@...t.ru>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        lvc-project@...uxtesting.org
Subject: Re: [lvc-project] [PATCH] netfilter: xt_recent: Fix attempt to
 update removed entry

Jan Engelhardt <jengelh@...i.de> wrote:
> On Thursday 2023-02-09 16:07, Florian Westphal wrote:
> 
> >Igor Artemiev <Igor.A.Artemiev@...t.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.