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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Wed, 1 Nov 2017 11:37:45 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r325276 - head/sys/dev/hwpmc
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Author: kib
Date: Wed Nov  1 11:37:45 2017
New Revision: 325276
URL: https://svnweb.freebsd.org/changeset/base/325276

Log:
  Be protective and check the po_file validity before dropping the ref.
  
  Reported and tested by:	pho
  Reviewed by:	markj
  Sponsored by:	The FreeBSD Foundation
  MFC after:	1 week
  X-Differential revision:	https://reviews.freebsd.org/D12882

Modified:
  head/sys/dev/hwpmc/hwpmc_logging.c

Modified: head/sys/dev/hwpmc/hwpmc_logging.c
==============================================================================
--- head/sys/dev/hwpmc/hwpmc_logging.c	Wed Nov  1 11:32:52 2017	(r325275)
+++ head/sys/dev/hwpmc/hwpmc_logging.c	Wed Nov  1 11:37:45 2017	(r325276)
@@ -681,8 +681,11 @@ pmclog_deconfigure_log(struct pmc_owner *po)
 	}
 
 	/* drop a reference to the fd */
-	error = fdrop(po->po_file, curthread);
-	po->po_file  = NULL;
+	if (po->po_file != NULL) {
+		error = fdrop(po->po_file, curthread);
+		po->po_file  = NULL;
+	} else
+		error = 0;
 	po->po_error = 0;
 
 	return (error);