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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Tue, 30 Dec 2008 12:51:56 +0000 (UTC)
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Subject: svn commit: r186601 - head/sys/kern
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Author: kib
Date: Tue Dec 30 12:51:56 2008
New Revision: 186601
URL: http://svn.freebsd.org/changeset/base/186601

Log:
  Clear the pointers to the file in the struct filedesc before file is closed
  in fdfree. Otherwise, sysctl_kern_proc_filedesc may dereference stale
  struct file * values.
  
  Reported and tested by:	pho
  MFC after:	1 month

Modified:
  head/sys/kern/kern_descrip.c

Modified: head/sys/kern/kern_descrip.c
==============================================================================
--- head/sys/kern/kern_descrip.c	Tue Dec 30 12:51:14 2008	(r186600)
+++ head/sys/kern/kern_descrip.c	Tue Dec 30 12:51:56 2008	(r186601)
@@ -1703,14 +1703,16 @@ fdfree(struct thread *td)
 	FILEDESC_XUNLOCK(fdp);
 	if (i > 0)
 		return;
-	/*
-	 * We are the last reference to the structure, so we can
-	 * safely assume it will not change out from under us.
-	 */
+
 	fpp = fdp->fd_ofiles;
 	for (i = fdp->fd_lastfile; i-- >= 0; fpp++) {
-		if (*fpp)
-			(void) closef(*fpp, td);
+		if (*fpp) {
+			FILEDESC_XLOCK(fdp);
+			fp = *fpp;
+			*fpp = NULL;
+			FILEDESC_XUNLOCK(fdp);
+			(void) closef(fp, td);
+		}
 	}
 	FILEDESC_XLOCK(fdp);