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To: Brooks Davis <brooks@one-eyed-alien.net>
References: <200409170741.i8H7fGV3011078@pooker.samsco.org>
	<20040917162535.GA5750@odin.ac.hmc.edu> <xzpu0twn5gz.fsf@dwp.des.no>
	<20040917184817.GA22747@odin.ac.hmc.edu>
From: des@des.no (=?iso-8859-1?q?Dag-Erling_Sm=F8rgrav?=)
Date: Fri, 17 Sep 2004 21:30:19 +0200
In-Reply-To: <20040917184817.GA22747@odin.ac.hmc.edu> (Brooks Davis's
 message of "Fri, 17 Sep 2004 11:48:17 -0700")
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cc: re@FreeBSD.org
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Subject: Re: 5.3-RELEASE TODO
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Brooks Davis <brooks@one-eyed-alien.net> writes:
> On Fri, Sep 17, 2004 at 07:57:32PM +0200, Dag-Erling Sm=F8rgrav wrote:
> >     struct sbuf *sb =3D sbuf_new(NULL, NULL, size, ifc->ifc_len + 1);
> What are you trying to do here?  Unless my manpages are wrong, the
> fourth arg is flags.  Do you mean to set SBUF_FIXEDLEN?

I meant

     struct sbuf *sb =3D sbuf_new(NULL, NULL, ifc->ifc_len + 1, SBUF_FIXEDL=
EN);

but I'm typing over a slow link and Meta-D'ed the wrong word.

>                                                          I think you
> would have to to avoid a new LOR.

Of course.

> would have to to avoid a new LOR.  Also, it is not safe to trust
> ifc->ifc_len for allocations because it is provided by potentially
> unpriveleged users.

so just make sure before you call sbuf_new() that ifc_len is
reasonable (e.g. < MAXPHYS)

>                      Thus, so you have to know how much space you will
> need before doing any kind of allocation, hence the double loop and the
> potential race.

Using sbufs removes the need for loop and greatly simplifies how you
deal with overflows.

DES
--=20
Dag-Erling Sm=F8rgrav - des@des.no