linux-kernel - Re: Fix signalfd interaction with thread-private signals

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Message-ID: <alpine.LFD.0.98.0706201035030.3593@woody.linux-foundation.org>
Date:	Wed, 20 Jun 2007 10:38:04 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...sign.ru>
cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Davide Libenzi <davidel@...ilserver.org>,
	Nicholas Miell <nmiell@...cast.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Fix signalfd interaction with thread-private signals



On Wed, 20 Jun 2007, Oleg Nesterov wrote:
> 
> Also, suppose that some thread does
> 
> 	for (;;)
> 		signal(SIGSEGV, SIG_IGN);
> 
> Now we have the same situation. do_sigaction() can steal SIGSEGV from
> another thread.

Actually, that shouldn't be possible.

See "force_sig_info()". It does not allow blocking or ignoring forced 
signals. We will reset such a signal handler to SIG_DFL, and unlock it.

So if you get a SIGSEGV while SIGSEGV's are blocked or ignored, the kernel 
*will* kill you. No questions asked.

		Linus
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