linux-kernel - [PATCH] sysctl: fix write access to dmesg_restrict/kptr

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Date:	Wed, 4 Apr 2012 11:40:19 -0700
From:	Kees Cook <keescook@...omium.org>
To:	"Serge E. Hallyn" <serge@...lyn.com>
Cc:	linux-kernel@...r.kernel.org, PhillipLougherplougher@...hat.com,
	Andrew Morton <akpm@...ux-foundation.org>,
	Richard Weinberger <richard@....at>,
	Greg Kroah-Hartman <greg@...ah.com>,
	Dan Rosenberg <drosenberg@...curity.com>,
	Eugene Teo <eteo@...hat.com>, Eric Paris <eparis@...hat.com>,
	James Morris <jmorris@...ei.org>
Subject: [PATCH] sysctl: fix write access to dmesg_restrict/kptr_restrict

Commit bfdc0b4 adds code to restrict access to dmesg_restrict,
however, it incorrectly alters kptr_restrict rather than
dmesg_restrict.

The original patch from Richard Weinberger
(https://lkml.org/lkml/2011/3/14/362) alters dmesg_restrict as
expected, and so the patch seems to have been misapplied.

This adds the CAP_SYS_ADMIN check to both dmesg_restrict and
kptr_restrict, since both are sensitive.

Reported-by: Phillip Lougher <plougher@...hat.com>
Signed-off-by: Kees Cook <keescook@...omium.org>
Cc: stable@...r.kernel.org
---
 kernel/sysctl.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 52b3a06..4ab1187 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -170,7 +170,7 @@ static int proc_taint(struct ctl_table *table, int write,
 #endif
 
 #ifdef CONFIG_PRINTK
-static int proc_dmesg_restrict(struct ctl_table *table, int write,
+static int proc_dointvec_minmax_sysadmin(struct ctl_table *table, int write,
 				void __user *buffer, size_t *lenp, loff_t *ppos);
 #endif
 
@@ -703,7 +703,7 @@ static struct ctl_table kern_table[] = {
 		.data		= &dmesg_restrict,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
+		.proc_handler	= proc_dointvec_minmax_sysadmin,
 		.extra1		= &zero,
 		.extra2		= &one,
 	},
@@ -712,7 +712,7 @@ static struct ctl_table kern_table[] = {
 		.data		= &kptr_restrict,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dmesg_restrict,
+		.proc_handler	= proc_dointvec_minmax_sysadmin,
 		.extra1		= &zero,
 		.extra2		= &two,
 	},
@@ -1943,7 +1943,7 @@ static int proc_taint(struct ctl_table *table, int write,
 }
 
 #ifdef CONFIG_PRINTK
-static int proc_dmesg_restrict(struct ctl_table *table, int write,
+static int proc_dointvec_minmax_sysadmin(struct ctl_table *table, int write,
 				void __user *buffer, size_t *lenp, loff_t *ppos)
 {
 	if (write && !capable(CAP_SYS_ADMIN))
-- 
1.7.0.4

-- 
Kees Cook
Chrome OS Security
--
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