linux-kernel - Re: [PATCH] perf/x86: fix broken LBR fixup code

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Message-ID: <1339422464.30462.17.camel@twins>
Date:	Mon, 11 Jun 2012 15:47:44 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Stephane Eranian <eranian@...gle.com>
Cc:	linux-kernel@...r.kernel.org, asharma@...com, mingo@...e.hu
Subject: Re: [PATCH] perf/x86: fix broken LBR fixup code

On Mon, 2012-06-11 at 15:44 +0200, Stephane Eranian wrote:
> I noticed that the LBR fixups were not working anymore
> on programs where they used to. I tracked this down to
> a recent change to copy_from_user_nmi().
> 
> commit db0dc75d6403b6663c0eab4c6ccb672eb9b2ed72
> Author: Arun Sharma <asharma@...com>
> Date:   Fri Apr 20 15:41:36 2012 -0700
> 
>     perf/x86: Check user address explicitly in copy_from_user_nmi()
>     
> This commit added a call to __range_not_ok() to the
> copy_from_user_nmi() routine. The problem is that the logic
> of the test must be reversed. __range_not_ok() returns 0 if the
> range is VALID. We want to return early from copy_from_user_nmi()
> if the range is NOT valid.

D'0h.. Thanks!
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