linux-kernel - Re: [PATCH 1/1] file capabilities: remove cap_task

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Date:	Wed, 19 Mar 2008 15:12:12 -0300
From:	"Luiz Fernando N. Capitulino" <lcapitulino@...driva.com.br>
To:	"Serge E. Hallyn" <serue@...ibm.com>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...l.org>,
	Andrew Morton <akpm@...l.org>,
	Andrew Morgan <morgan@...nel.org>, buraphalinuxserver@...il.com
Subject: Re: [PATCH 1/1] file capabilities: remove cap_task_kill() (-git)

Em Wed, 19 Mar 2008 11:56:35 -0500
"Serge E. Hallyn" <serue@...ibm.com> escreveu:

| (resending once against -git.  I had sent against -stable in
| http://lkml.org/lkml/2008/2/28/225.  Without this patch,
| atd is broken at least on some distros.)
| 
| The original justification for cap_task_kill() was as follows:
| 
| 	check_kill_permission() does appropriate uid equivalence checks.
| 	However with file capabilities it becomes possible for an
| 	unprivileged user to execute a file with file capabilities
| 	resulting in a more privileged task with the same uid.
| 
| However now that cap_task_kill() always returns 0 (permission
| granted) when p->uid==current->uid, the whole hook is worthless,
| and only likely to create more subtle problems in the corner cases
| where it might still be called but return -EPERM.  Those cases
| are basically when uids are different but euid/suid is equivalent
| as per the check in check_kill_permission().
| 
| One example of a still-broken application is 'at' for non-root users.
| 
| This patch removes cap_task_kill().
| 
| Signed-off-by: Serge Hallyn <serge@...lyn.com>
| Acked-by: Andrew G. Morgan <morgan@...nel.org>

 I've tested the -stable patch (no time to test this one, but it's
exactly the same patch), not sure if this applies to this but...

Tested-by: Luiz Fernando N. Capitulino <lcapitulino@...driva.com.br>

-- 
Luiz Fernando N. Capitulino
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