fix bogus reporting of signals by audit

Async signals should not be reported as sent by current in audit log.  As
it is, we call audit_signal_info() too early in check_kill_permission().
Note that check_kill_permission() has that test already - it needs to know
if it should apply current-based permission checks.  So the solution is to
move the call of audit_signal_info() between those.

Bogosity in question is easily reproduced - add a rule watching for e.g.
kill(2) from specific process (so that audit_signal_info() would not
short-circuit to nothing), say load_policy, watch the bogus OBJ_PID entry
in audit logs claiming that write(2) on selinuxfs file issued by
load_policy(8) had somehow managed to send a signal to syslogd...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Steve Grubb <sgrubb@redhat.com>
Acked-by: Eric Paris <eparis@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/kernel/signal.c b/kernel/signal.c
index 9fb91a3..7929523 100644 (file)
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -531,18 +531,18 @@ static int check_kill_permission(int sig, struct siginfo *info,
        if (!valid_signal(sig))
                return error;
 
-       error = audit_signal_info(sig, t); /* Let audit system see the signal */
-       if (error)
-               return error;
-
-       error = -EPERM;
-       if ((info == SEND_SIG_NOINFO || (!is_si_special(info) && SI_FROMUSER(info)))
-           && ((sig != SIGCONT) ||
-               (process_session(current) != process_session(t)))
-           && (current->euid ^ t->suid) && (current->euid ^ t->uid)
-           && (current->uid ^ t->suid) && (current->uid ^ t->uid)
-           && !capable(CAP_KILL))
+       if (info == SEND_SIG_NOINFO || (!is_si_special(info) && SI_FROMUSER(info))) {
+               error = audit_signal_info(sig, t); /* Let audit system see the signal */
+               if (error)
+                       return error;
+               error = -EPERM;
+               if (((sig != SIGCONT) ||
+                       (process_session(current) != process_session(t)))
+                   && (current->euid ^ t->suid) && (current->euid ^ t->uid)
+                   && (current->uid ^ t->suid) && (current->uid ^ t->uid)
+                   && !capable(CAP_KILL))
                return error;
+       }
 
        return security_task_kill(t, info, sig, 0);
 }