linux-kernel - Re: x86: get rid of the insane TIF_ABI

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20100216102332.GL21783@one.firstfloor.org>
Date:	Tue, 16 Feb 2010 11:23:32 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andi Kleen <andi@...stfloor.org>, "H. Peter Anvin" <hpa@...or.com>,
	Roland McGrath <roland@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: x86: get rid of the insane TIF_ABI_PENDING bit

On Tue, Feb 16, 2010 at 11:19:03AM +0100, Oleg Nesterov wrote:
> On 02/15, H. Peter Anvin wrote:
> >
> > On 02/15/2010 11:41 AM, Roland McGrath wrote:
> > > It affects whatever uses is_compat_task(), but I can't see anything
> > > where that matters except inside some particular syscall or for
> > > syscall restart after signals.
> >
> > FWIW, the origin of this is checkin
> > 4d9bc79cd28b779610d9590b3a96a28a0f64a25a (2.6.18-rc1), which somewhat
> > unhelpfully states "Make sure is_compat_task works early".  It doesn't
> > specify what the failure is if is_compat_task doesn't work early.
> 
> Perhaps Andi could explain us why this is needed,
> 
> > On
> > the other hand, it sure as heck seems better to set it and not need it
> > than the other way around.
> 
> Agreed, but otoh it is always good to understand the code. If we
> really have a reason for TS_COMPAT, a small comment can help other
> readers.

My memory is somewhat fuzzy on this one, but I think it was related
to VMA placement (probably for stack randomization or something like that)
This happens before the first call. I might be wrong on that.

There might also have been other is_compat_task checks in the exec init
path, so partly it was defensive programming.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/