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Date:      Sat, 24 Nov 2018 16:58:34 +0000 (UTC)
From:      Mark Johnston <markj@FreeBSD.org>
To:        src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org
Subject:   svn commit: r340898 - head/sys/kern
Message-ID:  <201811241658.wAOGwYdY002451@repo.freebsd.org>
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Author: markj
Date: Sat Nov 24 16:58:34 2018
New Revision: 340898
URL: https://svnweb.freebsd.org/changeset/base/340898

Log:
  Ensure that knotes do not get registered when KQ_CLOSING is set.
  
  KQ_CLOSING is set before draining the knotes associated with a kqueue,
  so we must ensure that new knotes are not added after that point.  In
  particular, some kernel facilities may register for events on behalf
  of a userspace process and race with a close of the kqueue.
  
  PR:		228858
  Reviewed by:	kib
  Tested by:	pho
  MFC after:	3 days
  Sponsored by:	The FreeBSD Foundation
  Differential Revision:	https://reviews.freebsd.org/D18316

Modified:
  head/sys/kern/kern_event.c

Modified: head/sys/kern/kern_event.c
==============================================================================
--- head/sys/kern/kern_event.c	Sat Nov 24 16:41:29 2018	(r340897)
+++ head/sys/kern/kern_event.c	Sat Nov 24 16:58:34 2018	(r340898)
@@ -1460,8 +1460,11 @@ findkn:
 					break;
 		}
 	} else {
-		if ((kev->flags & EV_ADD) == EV_ADD)
-			kqueue_expand(kq, fops, kev->ident, waitok);
+		if ((kev->flags & EV_ADD) == EV_ADD) {
+			error = kqueue_expand(kq, fops, kev->ident, waitok);
+			if (error != 0)
+				goto done;
+		}
 
 		KQ_LOCK(kq);
 
@@ -1693,12 +1696,12 @@ kqueue_expand(struct kqueue *kq, struct filterops *fop
 {
 	struct klist *list, *tmp_knhash, *to_free;
 	u_long tmp_knhashmask;
-	int size;
-	int fd;
+	int error, fd, size;
 	int mflag = waitok ? M_WAITOK : M_NOWAIT;
 
 	KQ_NOTOWNED(kq);
 
+	error = 0;
 	to_free = NULL;
 	if (fops->f_isfd) {
 		fd = ident;
@@ -1710,9 +1713,11 @@ kqueue_expand(struct kqueue *kq, struct filterops *fop
 			if (list == NULL)
 				return ENOMEM;
 			KQ_LOCK(kq);
-			if (kq->kq_knlistsize > fd) {
+			if ((kq->kq_state & KQ_CLOSING) != 0) {
 				to_free = list;
-				list = NULL;
+				error = EBADF;
+			} else if (kq->kq_knlistsize > fd) {
+				to_free = list;
 			} else {
 				if (kq->kq_knlist != NULL) {
 					bcopy(kq->kq_knlist, list,
@@ -1734,9 +1739,12 @@ kqueue_expand(struct kqueue *kq, struct filterops *fop
 			    &tmp_knhashmask,
 			    waitok ? HASH_WAITOK : HASH_NOWAIT);
 			if (tmp_knhash == NULL)
-				return ENOMEM;
+				return (ENOMEM);
 			KQ_LOCK(kq);
-			if (kq->kq_knhashmask == 0) {
+			if ((kq->kq_state & KQ_CLOSING) != 0) {
+				to_free = tmp_knhash;
+				error = EBADF;
+			} else if (kq->kq_knhashmask == 0) {
 				kq->kq_knhash = tmp_knhash;
 				kq->kq_knhashmask = tmp_knhashmask;
 			} else {
@@ -1748,7 +1756,7 @@ kqueue_expand(struct kqueue *kq, struct filterops *fop
 	free(to_free, M_KQUEUE);
 
 	KQ_NOTOWNED(kq);
-	return 0;
+	return (error);
 }
 
 static void
@@ -2597,6 +2605,8 @@ knote_attach(struct knote *kn, struct kqueue *kq)
 	KASSERT(kn_in_flux(kn), ("knote %p not marked influx", kn));
 	KQ_OWNED(kq);
 
+	if ((kq->kq_state & KQ_CLOSING) != 0)
+		return (EBADF);
 	if (kn->kn_fop->f_isfd) {
 		if (kn->kn_id >= kq->kq_knlistsize)
 			return (ENOMEM);

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