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Date:   Mon, 20 Mar 2023 23:10:22 +0100
From:   Florian Westphal <fw@strlen.de>
To:     Kyuwon Shim <Kyuwon.Shim@alliedtelesis.co.nz>
Cc:     "fw@strlen.de" <fw@strlen.de>,
        "pablo@netfilter.org" <pablo@netfilter.org>,
        "netfilter-devel@vger.kernel.org" <netfilter-devel@vger.kernel.org>
Subject: Re: [PATCH v2] ulogd2: Avoid use after free in unregister on global
 ulogd_fds linked list
Message-ID: <20230320221022.GA4659@breakpoint.cc>
References: <1678233154187.35009@alliedtelesis.co.nz>
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Kyuwon Shim <Kyuwon.Shim@alliedtelesis.co.nz> wrote:
> Hi, Florian
> This is valgrind logs.
> 
> ==4797== Memcheck, a memory error detector
> ==4797== Copyright (C) 2002-2022, and GNU GPL'd, by Julian Seward et
> al.
> ==4797== Using Valgrind-3.19.0 and LibVEX; rerun with -h for copyright
> info
> ==4797== Command: ulogd -v -c /etc/ulogd.conf
> ==4797== Invalid read of size 4
> ==4797==    at 0x405F60: ulogd_unregister_fd (select.c:74)
> ==4797==    by 0x4E4E3DF: ??? (in /usr/lib/ulogd/ulogd_inppkt_NFLOG.so)
> ==4797==    by 0x405003: stop_pluginstances (ulogd.c:1335)
> ==4797==    by 0x405003: sigterm_handler_task (ulogd.c:1383)
> ==4797==    by 0x405153: call_signal_handler_tasks (ulogd.c:424)
> ==4797==    by 0x405153: signal_channel_callback (ulogd.c:443)
> ==4797==    by 0x406163: ulogd_select_main (select.c:105)
> ==4797==    by 0x403CF3: ulogd_main_loop (ulogd.c:1070)
> ==4797==    by 0x403CF3: main (ulogd.c:1649)
> ==4797==  Address 0x4a84f40 is 160 bytes inside a block of size 4,848
> free'd

Yuck, thanks for the backtrace.  I've applied the patch with an amended
changelog and a comment wrt. ::stop doing such things.