linux-kernel - Re: [PATCH v2 08/10] x86-64: Emulate vsyscalls

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: <BANLkTi=aX5un5ZPVD9u6NRJb-koFG7T=6w@mail.gmail.com>
Date:	Mon, 30 May 2011 06:57:22 -0400
From:	Andrew Lutomirski <luto@....edu>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, Jesper Juhl <jj@...osbits.net>,
	Borislav Petkov <bp@...en8.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Jan Beulich <JBeulich@...ell.com>,
	richard -rw- weinberger <richard.weinberger@...il.com>,
	Mikael Pettersson <mikpe@...uu.se>
Subject: Re: [PATCH v2 08/10] x86-64: Emulate vsyscalls

On Mon, May 30, 2011 at 3:46 AM, Ingo Molnar <mingo@...e.hu> wrote:
>
> * Andy Lutomirski <luto@....EDU> wrote:
>
>> There's a fair amount of code in the vsyscall page, and who knows
>> what will happen if an exploit jumps into the middle of it.  Reduce
>> the risk by replacing most of it with short magic incantations that
>> are useless if entered in the middle.  This change can be disabled
>> by CONFIG_UNSAFE_VSYSCALLS (default y).
>
> btw., please flip the default or consider removing the option
> altogether.
>
> We want to improve security and we want safe vsyscalls the default,
> and it's no good if we make it too easy for users to keep the fire
> door open all the time! :-)

I'd advocate waiting until glibc 2.14 comes out with this change:

http://sourceware.org/git/?p=glibc.git;a=commit;h=a8509ca540427502bd955f35296ff7b727c7a8a1

I want to add a warning (ratelimited to an extremely low rate) in v3
whenever any of the vsyscalls get used telling users that their legacy
code is suffering a performance impact, but it seems like bad form to
tell people to build glibc from git to avoid a regression.

The other option is to make the change unconditional for gettimeofday
and vgetcpu but leave time alone for awhile.  There's no a priori
reason why leaving vtime around is worse than vread_tsc and
vread_hpet.


--Andy
--
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/