linux-kernel - Re: [PATCH 1/3] setup_arg_pages: diagnose excessive argument size

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Message-ID: <4C909193.2667.179386C9@pageexec.freemail.hu>
Date:	Wed, 15 Sep 2010 11:27:47 +0200
From:	pageexec@...email.hu
To:	Roland McGrath <roland@...hat.com>
CC:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Brad Spengler <spender@...ecurity.net>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, oss-security@...ts.openwall.com,
	Solar Designer <solar@...nwall.com>,
	Kees Cook <kees.cook@...onical.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	Oleg Nesterov <oleg@...hat.com>,
	Neil Horman <nhorman@...driver.com>,
	linux-fsdevel@...r.kernel.org, Eugene Teo <eugene@...hat.com>
Subject: Re: [PATCH 1/3] setup_arg_pages: diagnose excessive argument size

On 14 Sep 2010 at 16:04, Roland McGrath wrote:

> > userland could never rely on the kernel's policy at all since get_arg_page
> > could have failed for more reasons than overstepping the currently hardcoded
> > ARG_MAX check in there. 
> 
> I don't see how it could fail except for OOM cases where get_user_pages()
> failed rather than blocking.  Is that what you mean?

yes but it's not only OOM (ENOMEM from some allocation), but it can be also
EPERM from LSM (if mmap_min_addr is set too high) or EFAULT from get_user_pages
(e.g., if VM_FAULT_HWPOISON was returned for a requested page).

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