SELinux: Don't flush inherited SIGKILL during execve()
David Howells [Wed, 29 Apr 2009 12:45:05 +0000 (13:45 +0100)]
Don't flush inherited SIGKILL during execve() in SELinux's post cred commit
hook.  This isn't really a security problem: if the SIGKILL came before the
credentials were changed, then we were right to receive it at the time, and
should honour it; if it came after the creds were changed, then we definitely
should honour it; and in any case, all that will happen is that the process
will be scrapped before it ever returns to userspace.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>

include/linux/sched.h
kernel/signal.c
security/selinux/hooks.c

index 1d19c02..d3b787c 100644 (file)
@@ -1875,6 +1875,7 @@ extern void sched_dead(struct task_struct *p);
 
 extern void proc_caches_init(void);
 extern void flush_signals(struct task_struct *);
+extern void __flush_signals(struct task_struct *);
 extern void ignore_signals(struct task_struct *);
 extern void flush_signal_handlers(struct task_struct *, int force_default);
 extern int dequeue_signal(struct task_struct *tsk, sigset_t *mask, siginfo_t *info);
index 1c88144..f93efec 100644 (file)
@@ -238,14 +238,19 @@ void flush_sigqueue(struct sigpending *queue)
 /*
  * Flush all pending signals for a task.
  */
+void __flush_signals(struct task_struct *t)
+{
+       clear_tsk_thread_flag(t, TIF_SIGPENDING);
+       flush_sigqueue(&t->pending);
+       flush_sigqueue(&t->signal->shared_pending);
+}
+
 void flush_signals(struct task_struct *t)
 {
        unsigned long flags;
 
        spin_lock_irqsave(&t->sighand->siglock, flags);
-       clear_tsk_thread_flag(t, TIF_SIGPENDING);
-       flush_sigqueue(&t->pending);
-       flush_sigqueue(&t->signal->shared_pending);
+       __flush_signals(t);
        spin_unlock_irqrestore(&t->sighand->siglock, flags);
 }
 
index dd19ba8..5a34511 100644 (file)
@@ -2394,11 +2394,12 @@ static void selinux_bprm_committed_creds(struct linux_binprm *bprm)
                memset(&itimer, 0, sizeof itimer);
                for (i = 0; i < 3; i++)
                        do_setitimer(i, &itimer, NULL);
-               flush_signals(current);
                spin_lock_irq(&current->sighand->siglock);
-               flush_signal_handlers(current, 1);
-               sigemptyset(&current->blocked);
-               recalc_sigpending();
+               if (!(current->signal->flags & SIGNAL_GROUP_EXIT)) {
+                       __flush_signals(current);
+                       flush_signal_handlers(current, 1);
+                       sigemptyset(&current->blocked);
+               }
                spin_unlock_irq(&current->sighand->siglock);
        }