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From: Mark Johnston <markj@FreeBSD.org>
Date: Wed, 29 Nov 2017 19:47:09 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r326371 - head/sys/vm
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Author: markj
Date: Wed Nov 29 19:47:09 2017
New Revision: 326371
URL: https://svnweb.freebsd.org/changeset/base/326371

Log:
  Verify the object/vnode association after vget() in vm_pageout_clean().
  
  It's theoretically possible for the vnode and object to be disassociated
  while locks are dropped around the vget() call, in which case we
  shouldn't proceed with laundering.
  
  Noted and reviewed by:	kib
  MFC after:	1 week

Modified:
  head/sys/vm/vm_pageout.c

Modified: head/sys/vm/vm_pageout.c
==============================================================================
--- head/sys/vm/vm_pageout.c	Wed Nov 29 18:21:17 2017	(r326370)
+++ head/sys/vm/vm_pageout.c	Wed Nov 29 19:47:09 2017	(r326371)
@@ -647,7 +647,17 @@ vm_pageout_clean(vm_page_t m, int *numpagedout)
 			goto unlock_mp;
 		}
 		VM_OBJECT_WLOCK(object);
+
+		/*
+		 * Ensure that the object and vnode were not disassociated
+		 * while locks were dropped.
+		 */
+		if (vp->v_object != object) {
+			error = ENOENT;
+			goto unlock_all;
+		}
 		vm_page_lock(m);
+
 		/*
 		 * While the object and page were unlocked, the page
 		 * may have been: