lkml.org 
[lkml]   [2011]   [Mar]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[23/55] sysctl: restrict write access to dmesg_restrict
2.6.37-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Richard Weinberger <richard@nod.at>

commit bfdc0b497faa82a0ba2f9dddcf109231dd519fcc upstream.

When dmesg_restrict is set to 1 CAP_SYS_ADMIN is needed to read the kernel
ring buffer. But a root user without CAP_SYS_ADMIN is able to reset
dmesg_restrict to 0.

This is an issue when e.g. LXC (Linux Containers) are used and complete
user space is running without CAP_SYS_ADMIN. A unprivileged and jailed
root user can bypass the dmesg_restrict protection.

With this patch writing to dmesg_restrict is only allowed when root has
CAP_SYS_ADMIN.

Signed-off-by: Richard Weinberger <richard@nod.at>
Acked-by: Dan Rosenberg <drosenberg@vsecurity.com>
Acked-by: Serge E. Hallyn <serge@hallyn.com>
Cc: Eric Paris <eparis@redhat.com>
Cc: Kees Cook <kees.cook@canonical.com>
Cc: James Morris <jmorris@namei.org>
Cc: Eugene Teo <eugeneteo@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
kernel/sysctl.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)

--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -168,6 +168,11 @@ static int proc_taint(struct ctl_table *
void __user *buffer, size_t *lenp, loff_t *ppos);
#endif

+#ifdef CONFIG_PRINTK
+static int proc_dmesg_restrict(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos);
+#endif
+
#ifdef CONFIG_MAGIC_SYSRQ
/* Note: sysrq code uses it's own private copy */
static int __sysrq_enabled = SYSRQ_DEFAULT_ENABLE;
@@ -1469,7 +1474,7 @@ static struct ctl_table fs_table[] = {
.data = &suid_dumpable,
.maxlen = sizeof(int),
.mode = 0644,
- .proc_handler = proc_dointvec_minmax,
+ .proc_handler = proc_dmesg_restrict,
.extra1 = &zero,
.extra2 = &two,
},
@@ -2400,6 +2405,17 @@ static int proc_taint(struct ctl_table *
return err;
}

+#ifdef CONFIG_PRINTK
+static int proc_dmesg_restrict(struct ctl_table *table, int write,
+ void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+ if (write && !capable(CAP_SYS_ADMIN))
+ return -EPERM;
+
+ return proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+}
+#endif
+
struct do_proc_dointvec_minmax_conv_param {
int *min;
int *max;



\
 
 \ /
  Last update: 2011-03-26 01:25    [W:0.355 / U:1.200 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site