linux-kernel - Re: [PATCH v2] vsprintf: Check real user/group id for %pK

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Date:	Wed, 09 Oct 2013 07:57:56 -0700
From:	Joe Perches <joe@...ches.com>
To:	Dan Rosenberg <dan.j.rosenberg@...il.com>
Cc:	Ryan Mallon <rmallon@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	eldad@...refinery.com, Jiri Kosina <jkosina@...e.cz>,
	jgunthorpe@...idianresearch.com, Kees Cook <keescook@...omium.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	George Spelvin <linux@...izon.com>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] vsprintf: Check real user/group id for %pK

On Wed, 2013-10-09 at 07:14 -0400, Dan Rosenberg wrote:
> isn't the default value of kptr_restrict 0 now, unless I'm missing
> something? If I recall it was 1 when originally written, and then
> changed to 0 at some point. Could the documentation be updated to
> reflect that?

Yeah, the default got changed by
---------------------------
commit 411f05f123cbd7f8aa1edcae86970755a6e2a9d9
Author: Ingo Molnar <mingo@...e.hu>
Date:   Thu May 12 23:00:28 2011 +0200

kptr_restrict has been triggering bugs in apps such as perf, and it also makes
the system less useful by default, so turn it off by default.
---------------------------

Maybe this:
---
 Documentation/sysctl/kernel.txt | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 9d4c1d1..c17d5ca 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -289,14 +289,15 @@ Default value is "/sbin/hotplug".
 
 kptr_restrict:
 
-This toggle indicates whether restrictions are placed on
-exposing kernel addresses via /proc and other interfaces.  When
-kptr_restrict is set to (0), there are no restrictions.  When
-kptr_restrict is set to (1), the default, kernel pointers
-printed using the %pK format specifier will be replaced with 0's
-unless the user has CAP_SYSLOG.  When kptr_restrict is set to
-(2), kernel pointers printed using %pK will be replaced with 0's
-regardless of privileges.
+This toggle indicates whether restrictions are placed on exposing kernel
+addresses via /proc and other interfaces.
+
+When kptr_restrict is set to (0), the default, there are no restrictions.
+When kptr_restrict is set to (1), kernel pointers printed using the %pK
+format specifier will be replaced with 0's unless the user has CAP_SYSLOG
+and effective user and group ids are equal to the real ids.
+When kptr_restrict is set to (2), kernel pointers printed using %pK will
+be replaced with 0's regardless of privileges.
 
 ==============================================================
 


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