syslog: distinguish between /proc/kmsg and syscalls

This allows the LSM to distinguish between syslog functions originating
from /proc/kmsg access and direct syscalls.  By default, the commoncaps
will now no longer require CAP_SYS_ADMIN to read an opened /proc/kmsg
file descriptor.  For example the kernel syslog reader can now drop
privileges after opening /proc/kmsg, instead of staying privileged with
CAP_SYS_ADMIN.  MAC systems that implement security_syslog have unchanged
behavior.

Signed-off-by: Kees Cook <kees.cook@canonical.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Acked-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 3 insertions, 2 deletions

diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index 9a2ee845e9d4..a4862a0730fa 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -76,6 +76,7 @@
 #include <linux/selinux.h>
 #include <linux/mutex.h>
 #include <linux/posix-timers.h>
+#include <linux/syslog.h>
 
 #include "avc.h"
 #include "objsec.h"
@@ -2049,11 +2050,11 @@ static int selinux_quota_on(struct dentry *dentry)
         return dentry_has_perm(cred, NULL, dentry, FILE__QUOTAON);
 }
 
-static int selinux_syslog(int type)
+static int selinux_syslog(int type, bool from_file)
 {
         int rc;
 
-        rc = cap_syslog(type);
+        rc = cap_syslog(type, from_file);
         if (rc)
                 return rc;