path: root/Documentation
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authorDan Rosenberg <drosenberg@vsecurity.com>2010-11-11 14:05:18 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2010-11-12 07:55:32 -0800
commiteaf06b241b091357e72b76863ba16e89610d31bd (patch)
tree83bc8667309050b3538630707513574c14c51f37 /Documentation
parent203f40a5a030ed4048cd40e3bd9ab5df6c5df589 (diff)
Restrict unprivileged access to kernel syslog
The kernel syslog contains debugging information that is often useful during exploitation of other vulnerabilities, such as kernel heap addresses. Rather than futilely attempt to sanitize hundreds (or thousands) of printk statements and simultaneously cripple useful debugging functionality, it is far simpler to create an option that prevents unprivileged users from reading the syslog. This patch, loosely based on grsecurity's GRKERNSEC_DMESG, creates the dmesg_restrict sysctl. When set to "0", the default, no restrictions are enforced. When set to "1", only users with CAP_SYS_ADMIN can read the kernel syslog via dmesg(8) or other mechanisms. [akpm@linux-foundation.org: explain the config option in kernel.txt] Signed-off-by: Dan Rosenberg <drosenberg@vsecurity.com> Acked-by: Ingo Molnar <mingo@elte.hu> Acked-by: Eugene Teo <eugeneteo@kernel.org> Acked-by: Kees Cook <kees.cook@canonical.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'Documentation')
1 files changed, 14 insertions, 0 deletions
diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt
index 3894eaa2348..209e1584c3d 100644
--- a/Documentation/sysctl/kernel.txt
+++ b/Documentation/sysctl/kernel.txt
@@ -28,6 +28,7 @@ show up in /proc/sys/kernel:
- core_uses_pid
- ctrl-alt-del
- dentry-state
+- dmesg_restrict
- domainname
- hostname
- hotplug
@@ -213,6 +214,19 @@ to decide what to do with it.
+This toggle indicates whether unprivileged users are prevented from using
+dmesg(8) to view messages from the kernel's log buffer. When
+dmesg_restrict is set to (0) there are no restrictions. When
+dmesg_restrict is set set to (1), users must have CAP_SYS_ADMIN to use
+The kernel config option CONFIG_SECURITY_DMESG_RESTRICT sets the default
+value of dmesg_restrict.
domainname & hostname:
These files can be used to set the NIS/YP domainname and the