netdev - Re: nft 0.4, crash on list

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Date:	Sun, 22 Mar 2015 20:29:00 +0100
From:	Pablo Neira Ayuso <pablo@...filter.org>
To:	Denys Fedoryshchenko <nuclearcat@...learcat.com>
Cc:	Patrick McHardy <kaber@...sh.net>, Netdev <netdev@...r.kernel.org>,
	netfilter-devel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: nft 0.4, crash on list

On Sun, Mar 22, 2015 at 10:05:10AM +0200, Denys Fedoryshchenko wrote:
> On 2015-03-22 07:33, Patrick McHardy wrote:
> >On 22.03, Denys Fedoryshchenko wrote:
> >>Sorry for noise, seems git version working fine!
> >
> >Still this shouldn't be happening. Just to confirm, you were using an
> >unpatched kernel and by git you mean nftables git?
>
> Yes, correct. I tested on 3.18.8 and 3.19.2 vanilla kernels (x86_64).
> On nftables 0.4 it does crash, on nftables git it doesn't.

I sent this fix to -stable by March 10th but this doesn't show up in
3.18.x and 3.19.x yet.

[ upstream commit 02263db00b6cb98701332aa257c07ca549c2324b ]

We have several problems in this path:

1) There is a use-after-free when removing individual elements from
   the commit path.

2) We have to uninit() the data part of the element from the abort
   path to avoid a chain refcount leak.

3) We have to check for set->flags to see if there's a mapping,
instead
   of the element flags.

4) We have to check for !(flags & NFT_SET_ELEM_INTERVAL_END) to skip
   elements that are part of the interval that have no data part, so
   they don't need to be uninit().

Cc: <stable@...r.kernel.org> # 3.18.x
Cc: <stable@...r.kernel.org> # 3.19.x
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>

> >>On 2015-03-22 00:49, Denys Fedoryshchenko wrote:
> >>>Additionally, if i will do "nft flush table mangle" , with this table
> >>>added i will get this:
> >>>[   42.800078] ------------[ cut here ]------------
> >>>[   42.800092] WARNING: CPU: 3 PID: 2868 at
> >>>net/netfilter/nf_tables_api.c:4122 nft_data_uninit+0x35/0x50
> >>>[nf_tables]()
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