linux-kernel - Re: [3.1 patch] x86: default to vsyscall=native

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Message-ID: <CAFLxGvx0Cpu0ePytdCSSzfO2or3ZL3j5QrghOE5eWHZCJt6C6g@mail.gmail.com>
Date:	Thu, 6 Oct 2011 17:37:40 +0200
From:	richard -rw- weinberger <richard.weinberger@...il.com>
To:	Andrew Lutomirski <luto@....edu>
Cc:	Adrian Bunk <bunk@...sta.de>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [3.1 patch] x86: default to vsyscall=native

On Thu, Oct 6, 2011 at 5:06 AM, Andrew Lutomirski <luto@....edu> wrote:
> I'll see how ugly the patch to get this all correct is.  It may not be
> all that pretty because we won't be able to use sys_gettimeofday
> anymore.

BTW: The attached program triggers the issue.

on 3.1-rc8+:
# ./sig.dyn
faulting address: 0xdeadbeef
# ./sig.static
[   19.075106] sig.static[863] vsyscall fault (exploit attempt?)
ip:ffffffffff600000 cs:33 sp:7fff9e53d8c8 ax:ffffffffff600000 si:0
di:deadbeef
faulting address: 0x0

I guess UML is not the only user of this feature...

-- 
Thanks,
//richard

View attachment "sig.c" of type "text/x-csrc" (454 bytes)