linux-kernel - Re: [PATCH v3] fs: introduce pipe-only dump mode suid

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Date:	Sat, 23 Jun 2012 17:34:21 -0500
From:	Rob Landley <rob@...dley.net>
To:	Kees Cook <keescook@...omium.org>
CC:	linux-kernel@...r.kernel.org, Alan Cox <alan@...ux.intel.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Doug Ledford <dledford@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marcel Holtmann <marcel@...tmann.org>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	Joe Korty <joe.korty@...r.com>,
	David Howells <dhowells@...hat.com>,
	James Morris <james.l.morris@...cle.com>,
	linux-doc@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v3] fs: introduce pipe-only dump mode suid_dumpable=3

On 06/22/2012 02:24 PM, Kees Cook wrote:
> When the suid_dumpable sysctl is set to "2", and there is no core
> dump pipe defined in the core_pattern sysctl, a local user can cause
> core files to be written to root-writable directories, potentially with
> user-controlled content. This means an admin can unknowningly reintroduce
> a variation of CVE-2006-2451.
...
> --- a/Documentation/sysctl/fs.txt
> +++ b/Documentation/sysctl/fs.txt
> @@ -167,12 +167,12 @@ or otherwise protected/tainted binaries. The modes are
>  1 - (debug) - all processes dump core when possible. The core dump is
>  	owned by the current user and no security is applied. This is
>  	intended for system debugging situations only. Ptrace is unchecked.
> -2 - (suidsafe) - any binary which normally would not be dumped is dumped
> -	readable by root only. This allows the end user to remove
> -	such a dump but not access it directly. For security reasons
> -	core dumps in this mode will not overwrite one another or
> -	other files. This mode is appropriate when administrators are
> -	attempting to debug problems in a normal environment.
> +2 - (suidsafe) - no longer allowed (returns -EINVAL).

Random comment: a reference to the CVE might be good here.

Rob
-- 
GNU/Linux isn't: Linux=GPLv2, GNU=GPLv3+, they can't share code.
Either it's "mere aggregation", or a license violation.  Pick one.
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