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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Fri, 3 Mar 2017 10:17:16 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r314590 - stable/10/sys/vm
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Author: kib
Date: Fri Mar  3 10:17:16 2017
New Revision: 314590
URL: https://svnweb.freebsd.org/changeset/base/314590

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

Modified:
  stable/10/sys/vm/vm_fault.c
Directory Properties:
  stable/10/   (props changed)

Modified: stable/10/sys/vm/vm_fault.c
==============================================================================
--- stable/10/sys/vm/vm_fault.c	Fri Mar  3 10:02:56 2017	(r314589)
+++ stable/10/sys/vm/vm_fault.c	Fri Mar  3 10:17:16 2017	(r314590)
@@ -1140,11 +1140,12 @@ 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;
 	}
 
 	/*