linux-kernel - Re: [PATCH 1/5] signal(x86_32): Improve the signal stack overflow check

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Message-ID: <47BB977D.5090406@cn.fujitsu.com>
Date:	Wed, 20 Feb 2008 10:59:09 +0800
From:	Shi Weihua <shiwh@...fujitsu.com>
To:	Roland McGrath <roland@...hat.com>
CC:	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 1/5] signal(x86_32): Improve the signal stack overflow
 check

Roland McGrath wrote::
>> I spent some time read you mail carefully and dig into the code again.
>>
>> And yes, you are right. It's possible that SA_ONSTACK has been cleared
>> before the second signal on the same stack comes.
> 
> It's not necessary for SA_ONSTACK to have "been cleared", by which I assume
> you mean a sigaction call with SA_ONSTACK not set in sa_flags.  That is
> indeed possible, but it's not the only case your patch broke.  It can just
> be a different signal whose sigaction never had SA_ONSTACK, when you are
> still on the signal stack from an earlier signal that did have SA_ONSTACK.

Thanks for your explanation.

> 
>> So this patch is wrong  :( . I will revise the other 4 patches.
> 
> For 2 and 3, I would rather just wait until we unify signal.c anyway.

Ok. I see.

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