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Date:      Fri, 15 May 2015 14:15:18 +0200
From:      Julien Charbon <jch@freebsd.org>
To:        freebsd-net@freebsd.org
Cc:        John Baldwin <jhb@freebsd.org>, Jason Wolfe <nitroboost@gmail.com>, hiren panchasara <hiren@freebsd.org>, Sean Chittenden <sean@chittenden.org>
Subject:   Re: MFC-ing TCP timer race condition fix
Message-ID:  <5555E356.8080000@freebsd.org>
In-Reply-To: <5548EC8F.3010103@freebsd.org>
References:  <5548BB20.2020700@freebsd.org> <5548EC8F.3010103@freebsd.org>

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 Hi,

On 05/05/15 18:15, Julien Charbon wrote:
>  I was asked if it is possible to MFC r281599 in FreeBSD 10:
>=20
> ---
> Fix an old and well-documented use-after-free race condition in
> TCP timers:
>  - Add a reference from tcpcb to its inpcb
>  - Defer tcpcb deletion until TCP timers have finished
> ---
> https://svnweb.freebsd.org/base?view=3Drevision&revision=3D281599
>=20
>  First, I thought it was no possible as it touches struct
> tcp_timer/struct tcpcb_mem.  Second, John pointed me that these two
> structures are used only internally.  The only side effect I was able t=
o
> find is the increase of struct tcpcb_mem size:
>=20
>  - stable/10:                    struct tcpcb_mem size is 1024 bytes
>  - stable/10 + tcp timer change: struct tcpcb_mem size is 1032 bytes
>  - currently in head:            struct tcpcb_mem size is 1048 bytes
>=20
>  If you have extra concerns on MFC-ing this change please scream.
> Without nice yelps I plan to "MFC after: 1 month" (around May 16th).

 Following the lack of screamed concerns, here the MFC-ing result in
stable/10 of the old and well-documented use-after-free TCP timer race
condition fix:

https://svnweb.freebsd.org/base?view=3Drevision&revision=3D282964

 Thanks again John for your inputs about the feasibility of this MFC.

--
Julien


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