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

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Date:	Fri, 26 Jun 2009 18:48:19 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Neil Horman <nhorman@...driver.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 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 ?

Oleg.

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