linux-kernel - Re: [PATCH 2/2] exec: Make do_coredump more robust and safer when using pipes in core

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Message-ID: <20090626202045.GG7337@hmsreliant.think-freely.org>
Date:	Fri, 26 Jun 2009 16:20:45 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, earl_chew@...lent.com,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH 2/2] exec: Make do_coredump more robust and safer when
	using pipes in core_pattern: wait for core collectors

On Fri, Jun 26, 2009 at 06:48:19PM +0200, Oleg Nesterov wrote:
> On 06/26, Neil Horman wrote:
> >
> > - 		if (call_usermodehelper_pipe(corename+1, helper_argv, NULL,
> > -				&file)) {
> > + 		if (call_usermodehelper_pipe(helper_argv[0], helper_argv, NULL,
> > +				&file, &pid) < 0) {
> 
> ...
> 
> 
> > +	if (ispipe && core_pipe_limit)
> > +		sys_wait4(pid, NULL, 0, NULL);
> 
> How this can work? sys_wait4() can only wait for our childs, but the parent
> of the dumping thread is khelper.
> 
> 
> If we change kmod.c, then I think we need UMH_WAIT_CUSTOM_COMPLETION.
> 
> 
> But perhaps do_coredump() can just sleep on file->...->i_pipe->wait waiting
> for pipe_inode_info->readers == 0 ?
> 
Thats a good idea, I like that better.  I'll fix that up and repost monday
morning.
Neil

> Oleg.
> 
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