linux-kernel - Re: [PATCH 0/2] x86 vdso 32-bit vdso-disabling fixes

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Message-ID: <20080409084200.GA32466@elte.hu>
Date:	Wed, 9 Apr 2008 10:42:00 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Roland McGrath <roland@...hat.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Amnon Shiloh <u3557@...o.sublimeip.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] x86 vdso 32-bit vdso-disabling fixes


* Roland McGrath <roland@...hat.com> wrote:

> These two patches together address two potential bugs when trying to 
> disable the 32-bit vDSO via sysctl or boot parameters (vdso32=0).
> 
> Currently, every 32-bit exec gets the vDSO mapped even if it's 
> disabled (the process just doesn't get told about it).  Because it's 
> in fact always there, the bug that patch 1/2 fixes cannot happen now.  
> With patch 2/2, it won't be mapped at all when it's disabled, which is 
> one of the things that people might really want when they disable it 
> (so nothing they didn't ask for goes into their address space).
> 
> The 32-bit signal handler setup when SA_RESTORER is not used refers to 
> current->mm->context.vdso without regard to whether the vDSO has been 
> disabled when the process was exec'd.  Patch 1/2 fixes this not to use 
> it when it's null, which becomes possible after patch 2/2.  (This 
> never happens in normal use, because glibc's sigaction call uses 
> SA_RESTORER unless glibc detected the vDSO.)

thanks Roland, applied.

	Ingo
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