kqueue: Fix delivery of unwanted events

In both procdesc_kqops_event() and filt_proc(), the event variable can
have more than one bit set.  This means that:

* We cannot compare it directly with NOTE_EXIT; we must binary-and them
  instead.

* We cannot binary-or it with the report mask; we must binary-and it
  with the request mask first.

MFC after:	1 week
Fixes:		2a5e58c59694 ("procdesc: add NOTE_PDSIGCHLD")
Fixes:		b328975b9d7c ("procdesc: report NOTE_PDSIGCHLD for traced and stopped process")
Reviewed by:	kib, markj
Differential Revision:	https://reviews.freebsd.org/D58395

2 files changed, 5 insertions, 5 deletions

diff --git a/sys/kern/kern_event.c b/sys/kern/kern_event.c
index fa7f8bf7cdb7..e19415c8d443 100644
--- a/sys/kern/kern_event.c
+++ b/sys/kern/kern_event.c
@@ -529,11 +529,11 @@ filt_proc(struct knote *kn, long hint)
 	event = (u_int)hint & NOTE_PCTRLMASK;
 
 	/* If the user is interested in this event, record it. */
-	if (kn->kn_sfflags & event)
-		kn->kn_fflags |= event;
+	if ((kn->kn_sfflags & event) != 0)
+		kn->kn_fflags |= kn->kn_sfflags & event;
 
 	/* Process is gone, so flag the event as finished. */
-	if (event == NOTE_EXIT) {
+	if ((event & NOTE_EXIT) != 0) {
 		kn->kn_flags |= EV_EOF | EV_ONESHOT;
 		kn->kn_ptr.p_proc = NULL;
 		if (kn->kn_fflags & NOTE_EXIT)
diff --git a/sys/kern/sys_procdesc.c b/sys/kern/sys_procdesc.c
index 94c2df4b1e69..7fc63256bc05 100644
--- a/sys/kern/sys_procdesc.c
+++ b/sys/kern/sys_procdesc.c
@@ -518,8 +518,8 @@ procdesc_kqops_event(struct knote *kn, long hint)
 	}
 
 	/* If the user is interested in this event, record it. */
-	if (kn->kn_sfflags & event)
-		kn->kn_fflags |= event;
+	if ((kn->kn_sfflags & event) != 0)
+		kn->kn_fflags |= kn->kn_sfflags & event;
 
 	/* Process is gone, so flag the event as finished. */
 	if ((event & NOTE_EXIT) != 0) {