From: Aaron Conole <aconole@bytheb.org>
To: Liping Zhang <zlpnobody@gmail.com>
Cc: Feng Gao <gfree.wind@gmail.com>,
Netfilter Developer Mailing List
<netfilter-devel@vger.kernel.org>,
Linux Kernel Network Developers <netdev@vger.kernel.org>,
Florian Westphal <fw@strlen.de>,
Pablo Neira Ayuso <pablo@netfilter.org>
Subject: Re: [PATCH nf-next v2 1/2] netfilter: Fix potential null pointer dereference
Date: Wed, 28 Sep 2016 09:30:36 -0400 [thread overview]
Message-ID: <f7tponokv7n.fsf@redhat.com> (raw)
In-Reply-To: <CAML_gOeqjO--cPu=vt+ed14NqXP1uU41J0RDg5Up7xM79SCWjQ@mail.gmail.com> (Liping Zhang's message of "Wed, 28 Sep 2016 11:13:07 +0800")
Liping Zhang <zlpnobody@gmail.com> writes:
> 2016-09-28 11:08 GMT+08:00 Liping Zhang <zlpnobody@gmail.com>:
>> Hi Feng,
>>
>> 2016-09-28 9:23 GMT+08:00 Feng Gao <gfree.wind@gmail.com>:
>>> Hi Aaraon,
>>>
>>> On Tue, Sep 27, 2016 at 9:38 PM, Aaron Conole <aconole@bytheb.org> wrote:
>>>> It's possible for nf_hook_entry_head to return NULL if two
>>>> nf_unregister_net_hook calls happen simultaneously with a single hook
>>>
>>> The critical region of nf_unregister_net_hook is protected by &nf_hook_mutex.
>>> When it would be called simultaneously?
>>
>> This is unrelated to race condition.
>>
>> Suppose that only the last nf_hook_entry exist, and two callers want to do
>> un-register work.
>>
>> The first one will remove it successfully, after the end of the work, the
>> second one will enter the critical section, but it will see the NULL pointer.
>> Because the last nf_hook_entry was already removed by the first one.
>>
>>>
>>> Regards
>>> Feng
>>>
>>>> entry in the list. This fix ensures that no null pointer dereference
>>>> could occur when such a race happens.
>>>>
>>>> Signed-off-by: Aaron Conole <aconole@bytheb.org>
>
> I read the commit log again, I think the description here is a
> little confusing indeed.
Sorry about that. I've posted a new description which describes the
situation better. I hope it helps.
-Aaron
next prev parent reply other threads:[~2016-09-28 13:30 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-27 13:38 [PATCH nf-next v2 0/2] fixes for recent nf_compact hooks Aaron Conole
2016-09-27 13:38 ` [PATCH nf-next v2 1/2] netfilter: Fix potential null pointer dereference Aaron Conole
2016-09-28 1:23 ` Feng Gao
2016-09-28 3:08 ` Liping Zhang
2016-09-28 3:13 ` Liping Zhang
2016-09-28 7:56 ` Feng Gao
2016-09-28 13:30 ` Aaron Conole [this message]
2016-09-27 13:38 ` [PATCH nf-next v2 2/2] nf_set_hooks_head: acommodate different kconfig Aaron Conole
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=f7tponokv7n.fsf@redhat.com \
--to=aconole@bytheb.org \
--cc=fw@strlen.de \
--cc=gfree.wind@gmail.com \
--cc=netdev@vger.kernel.org \
--cc=netfilter-devel@vger.kernel.org \
--cc=pablo@netfilter.org \
--cc=zlpnobody@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.