linux-kernel - Re: [PATCH x86#core/percpu] x86: fix x86

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Date:	Wed, 11 Feb 2009 11:34:56 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Tejun Heo <tj@...nel.org>
Cc:	Brian Gerst <brgerst@...il.com>, hpa@...or.com, jeremy@...p.org,
	tglx@...utronix.de, linux-kernel@...r.kernel.org, x86@...nel.org,
	rusty@...tcorp.com.au
Subject: Re: [PATCH x86#core/percpu] x86: fix x86_32 stack protector bugs


* Tejun Heo <tj@...nel.org> wrote:

> Impact: fix x86_32 stack protector
> 
> Brian Gerst found out that %gs was being initialized to stack_canary
> instead of stack_canary - 20, which basically gave the same canary
> value for all threads.  Fixing this also exposed the following bugs.
> 
> * cpu_idle() didn't call boot_init_stack_canary()
> 
> * stack canary switching in switch_to() was being done too late making
>   the initial run of a new thread use the old stack canary value.
> 
> Fix all of them and while at it update comment in cpu_idle() about
> calling boot_init_stack_canary().
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> Reported-by: Brian Gerst <brgerst@...il.com>
> ---
>  arch/x86/include/asm/stackprotector.h |    2 +-
>  arch/x86/include/asm/system.h         |    8 +++-----
>  arch/x86/kernel/head_32.S             |    1 +
>  arch/x86/kernel/process_32.c          |   10 ++++++++++
>  arch/x86/kernel/process_64.c          |   11 +++++------
>  5 files changed, 20 insertions(+), 12 deletions(-)

Applied to tip:core/percpu, thanks guys!

I never got around to finding his bug in practice as the latest bits of 
tip:core/percpu are not in tip/master at the moment, due to that 64-bit
build failure.

	Ingo
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