[PATCH 3.12 105/212] audit: printk USER_AVC messages when audit isnt enabled

[Greg Kroah-Hartman]

3.12-stable review patch.  If anyone has any objections, please let me know.

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

From: Tyler Hicks <tyhicks at canonical.com>

commit 0868a5e150bc4c47e7a003367cd755811eb41e0b upstream.

When the audit=1 kernel parameter is absent and auditd is not running,
AUDIT_USER_AVC messages are being silently discarded.

AUDIT_USER_AVC messages should be sent to userspace using printk(), as
mentioned in the commit message of 4a4cd633 ("AUDIT: Optimise the
audit-disabled case for discarding user messages").

When audit_enabled is 0, audit_receive_msg() discards all user messages
except for AUDIT_USER_AVC messages. However, audit_log_common_recv_msg()
refuses to allocate an audit_buffer if audit_enabled is 0. The fix is to
special case AUDIT_USER_AVC messages in both functions.

It looks like commit 50397bd1 ("[AUDIT] clean up audit_receive_msg()")
introduced this bug.

Signed-off-by: Tyler Hicks <tyhicks at canonical.com>
Cc: Al Viro <viro at zeniv.linux.org.uk>
Cc: Eric Paris <eparis at redhat.com>
Cc: linux-audit at redhat.com
Acked-by: Kees Cook <keescook at chromium.org>
Signed-off-by: Richard Guy Briggs <rgb at redhat.com>
Signed-off-by: Eric Paris <eparis at redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>

---
 kernel/audit.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -613,7 +613,7 @@ static int audit_log_common_recv_msg(str
 	int rc = 0;
 	uid_t uid = from_kuid(&init_user_ns, current_uid());
 
-	if (!audit_enabled) {
+	if (!audit_enabled && msg_type != AUDIT_USER_AVC) {
 		*ab = NULL;
 		return rc;
 	}