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

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Message-Id: <20080220024928.0EE172701BA@magilla.localdomain>
Date:	Tue, 19 Feb 2008 18:49:28 -0800 (PST)
From:	Roland McGrath <roland@...hat.com>
To:	Shi Weihua <shiwh@...fujitsu.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

> 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.

> 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.

Thanks,
Roland
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