svn commit: r270443 - head/sys/kern

[Mateusz Guzik]

Author: mjg
Date: Sun Aug 24 09:02:16 2014
New Revision: 270443
URL: http://svnweb.freebsd.org/changeset/base/270443

Log:
  Properly reparent traced processes when the tracer dies.
  
  Previously they were uncoditionally reparented to init. In effect
  it was possible that tracee was never returned to original parent.
  
  Reviewed by:	kib
  MFC after:	1 week

Modified:
  head/sys/kern/kern_exit.c

Modified: head/sys/kern/kern_exit.c
==============================================================================
--- head/sys/kern/kern_exit.c	Sun Aug 24 08:03:59 2014	(r270442)
+++ head/sys/kern/kern_exit.c	Sun Aug 24 09:02:16 2014	(r270443)
@@ -156,7 +156,8 @@ sys_sys_exit(struct thread *td, struct s
 void
 exit1(struct thread *td, int rv)
 {
-	struct proc *p, *nq, *q;
+	struct proc *p, *nq, *q, *t;
+	struct thread *tdt;
 	struct vnode *ttyvp = NULL;
 
 	mtx_assert(&Giant, MA_NOTOWNED);
@@ -437,7 +438,9 @@ exit1(struct thread *td, int rv)
 	WITNESS_WARN(WARN_PANIC, NULL, "process (pid %d) exiting", p->p_pid);
 
 	/*
-	 * Reparent all of our children to init.
+	 * Reparent all children processes:
+	 * - traced ones to the original parent (or init if we are that parent)
+	 * - the rest to init
 	 */
 	sx_xlock(&proctree_lock);
 	q = LIST_FIRST(&p->p_children);
@@ -446,15 +449,23 @@ exit1(struct thread *td, int rv)
 	for (; q != NULL; q = nq) {
 		nq = LIST_NEXT(q, p_sibling);
 		PROC_LOCK(q);
-		proc_reparent(q, initproc);
 		q->p_sigparent = SIGCHLD;
-		/*
-		 * Traced processes are killed
-		 * since their existence means someone is screwing up.
-		 */
-		if (q->p_flag & P_TRACED) {
-			struct thread *temp;
 
+		if (!(q->p_flag & P_TRACED)) {
+			proc_reparent(q, initproc);
+		} else {
+			/*
+			 * Traced processes are killed since their existence
+			 * means someone is screwing up.
+			 */
+			t = proc_realparent(q);
+			if (t == p) {
+				proc_reparent(q, initproc);
+			} else {
+				PROC_LOCK(t);
+				proc_reparent(q, t);
+				PROC_UNLOCK(t);
+			}
 			/*
 			 * Since q was found on our children list, the
 			 * proc_reparent() call moved q to the orphan
@@ -463,8 +474,8 @@ exit1(struct thread *td, int rv)
 			 */
 			clear_orphan(q);
 			q->p_flag &= ~(P_TRACED | P_STOPPED_TRACE);
-			FOREACH_THREAD_IN_PROC(q, temp)
-				temp->td_dbgflags &= ~TDB_SUSPEND;
+			FOREACH_THREAD_IN_PROC(q, tdt)
+				tdt->td_dbgflags &= ~TDB_SUSPEND;
 			kern_psignal(q, SIGKILL);
 		}
 		PROC_UNLOCK(q);