svn commit: r314589 - stable/11/sys/vm

[Konstantin Belousov]

Author: kib
Date: Fri Mar  3 10:02:56 2017
New Revision: 314589
URL: https://svnweb.freebsd.org/changeset/base/314589

Log:
  MFC r314195:
  Properly handle possible underflow in vm_fault_prefault().

Modified:
  stable/11/sys/vm/vm_fault.c
Directory Properties:
  stable/11/   (props changed)

Modified: stable/11/sys/vm/vm_fault.c
==============================================================================
--- stable/11/sys/vm/vm_fault.c	Fri Mar  3 08:13:45 2017	(r314588)
+++ stable/11/sys/vm/vm_fault.c	Fri Mar  3 10:02:56 2017	(r314589)
@@ -1372,11 +1372,12 @@ vm_fault_prefault(const struct faultstat
 
 	entry = fs->entry;
 
-	starta = addra - backward * PAGE_SIZE;
-	if (starta < entry->start) {
+	if (addra < backward * PAGE_SIZE) {
 		starta = entry->start;
-	} else if (starta > addra) {
-		starta = 0;
+	} else {
+		starta = addra - backward * PAGE_SIZE;
+		if (starta < entry->start)
+			starta = entry->start;
 	}
 
 	/*