From: Jim Sansing <jjsansing@verizon•net>
To: Eric Dumazet <eric.dumazet@gmail•com>
Cc: Linux Network Development list <netdev@vger•kernel.org>
Subject: Re: Comment on nf_queue NF_STOLEN patch
Date: Tue, 18 Oct 2011 17:34:35 -0400 [thread overview]
Message-ID: <4E9DF0EB.8080008@verizon.net> (raw)
In-Reply-To: <1318973032.19139.5.camel@edumazet-laptop>
Eric Dumazet wrote:
> Le mardi 18 octobre 2011 à 15:08 -0400, Jim Sansing a écrit :
>
>> I have been working on a kernel module that registers with netfilter,
>> and I noticed that a patch was added to nf_queue that changed the
>> handling of return code NF_FILTER from 'do nothing' to 'free the skb'.
>> I'm not sure which kernel version this went in, but the date of the
>> patch is Feb, 19, 2010.
>>
>> Everything I have read about netfilter states that it is up to the
>> netfilter hook to free the skb if NF_STOLEN is returned. The
>> implications of this patch from a hook programming perspective are:
>>
>> 1) If the skb is used after the return from the hook, it must be cloned.
>> 2) The original skb must not be freed.
>>
>> I suggest that a comment be added to include/linux/netfilter.h that says
>> explicitly the skb will be freed if NF_STOLEN is returned.
>>
>
> But its not true. Just read the code.
>
> If you are working on this stuff I recommend you take a look at
> commits :
>
> c6675233f9015d3c0460c8aab53ed9b99d915c64
> (netfilter: nf_queue: reject NF_STOLEN verdicts from userspace)
>
> fad54440438a7c231a6ae347738423cbabc936d9
> (netfilter: avoid double free in nf_reinject)
>
> 64507fdbc29c3a622180378210ecea8659b14e40
> (netfilter: nf_queue: fix NF_STOLEN skb leak)
>
> 3bc38712e3a6e0596ccb6f8299043a826f983701
> ([NETFILTER]: nf_queue: handle NF_STOP and unknown verdicts in
> nf_reinject)
>
>
I see that fad54440438a7c231a6ae347738423cbabc936d9 (netfilter: avoid
double free in nf_reinject) returns the switch case for NF_STOLEN back
to the original state, but I just downloaded 3.0.4, and the skb is still
freed. So for some versions of the kernel, the situation exists.
Hopefully anyone who runs into it will find this thread.
Later . . . Jim
next prev parent reply other threads:[~2011-10-18 23:17 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-14 19:18 Problem with ixgbe and TX locked on one cpu Paweł Staszewski
2011-10-18 18:57 ` Jesse Brandeburg
2011-10-18 19:08 ` Comment on nf_queue NF_STOLEN patch Jim Sansing
2011-10-18 21:23 ` Eric Dumazet
2011-10-18 21:34 ` Jim Sansing [this message]
2011-10-19 4:10 ` Eric Dumazet
2011-10-20 10:30 ` Pablo Neira Ayuso
2011-10-19 9:21 ` Problem with ixgbe and TX locked on one cpu Paweł Staszewski
2011-10-19 9:21 ` Paweł Staszewski
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=4E9DF0EB.8080008@verizon.net \
--to=jjsansing@verizon$(echo .)net \
--cc=eric.dumazet@gmail$(echo .)com \
--cc=netdev@vger$(echo .)kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox