svn commit: r353930 - head/sys/kern

[Konstantin Belousov]

Author: kib
Date: Wed Oct 23 16:06:47 2019
New Revision: 353930
URL: https://svnweb.freebsd.org/changeset/base/353930

Log:
  Fix undefined behavior.
  
  Create a sequence point by ending a full expression for call to
  vspace() and use of the globals which are modified by vspace().
  
  Reported and reviewed by:	imp
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week
  Differential revision:	https://reviews.freebsd.org/D22126

Modified:
  head/sys/kern/vfs_subr.c

Modified: head/sys/kern/vfs_subr.c
==============================================================================
--- head/sys/kern/vfs_subr.c	Wed Oct 23 16:05:52 2019	(r353929)
+++ head/sys/kern/vfs_subr.c	Wed Oct 23 16:06:47 2019	(r353930)
@@ -1273,7 +1273,7 @@ vnlru_proc(void)
 {
 	struct mount *mp, *nmp;
 	unsigned long onumvnodes;
-	int done, force, trigger, usevnodes;
+	int done, force, trigger, usevnodes, vsp;
 	bool reclaim_nc_src;
 
 	EVENTHANDLER_REGISTER(shutdown_pre_sync, kproc_shutdown, vnlruproc,
@@ -1301,7 +1301,8 @@ vnlru_proc(void)
 			force = 1;
 			vstir = 0;
 		}
-		if (vspace() >= vlowat && force == 0) {
+		vsp = vspace();
+		if (vsp >= vlowat && force == 0) {
 			vnlruproc_sig = 0;
 			wakeup(&vnlruproc_sig);
 			msleep(vnlruproc, &vnode_free_list_mtx,
@@ -1368,7 +1369,8 @@ vnlru_proc(void)
 		 * After becoming active to expand above low water, keep
 		 * active until above high water.
 		 */
-		force = vspace() < vhiwat;
+		vsp = vspace();
+		force = vsp < vhiwat;
 	}
 }
 
@@ -1447,8 +1449,10 @@ vtryrecycle(struct vnode *vp)
 static void
 vcheckspace(void)
 {
+	int vsp;
 
-	if (vspace() < vlowat && vnlruproc_sig == 0) {
+	vsp = vspace();
+	if (vsp < vlowat && vnlruproc_sig == 0) {
 		vnlruproc_sig = 1;
 		wakeup(vnlruproc);
 	}