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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 /security/commoncap.c
parent203f40a5a030ed4048cd40e3bd9ab5df6c5df589 (diff)
downloadlinux-stericsson-eaf06b241b091357e72b76863ba16e89610d31bd.tar.gz
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 'security/commoncap.c')
-rw-r--r--security/commoncap.c2
1 files changed, 2 insertions, 0 deletions
diff --git a/security/commoncap.c b/security/commoncap.c
index 5e632b4857e4..04b80f9912bf 100644
--- a/security/commoncap.c
+++ b/security/commoncap.c
@@ -895,6 +895,8 @@ int cap_syslog(int type, bool from_file)
{
if (type != SYSLOG_ACTION_OPEN && from_file)
return 0;
+ if (dmesg_restrict && !capable(CAP_SYS_ADMIN))
+ return -EPERM;
if ((type != SYSLOG_ACTION_READ_ALL &&
type != SYSLOG_ACTION_SIZE_BUFFER) && !capable(CAP_SYS_ADMIN))
return -EPERM;