From owner-svn-src-head@freebsd.org  Mon Jul  6 16:07:22 2015
Return-Path: <owner-svn-src-head@freebsd.org>
Delivered-To: svn-src-head@mailman.ysv.freebsd.org
Received: from mx1.freebsd.org (mx1.freebsd.org
 [IPv6:2001:1900:2254:206a::19:1])
 by mailman.ysv.freebsd.org (Postfix) with ESMTP id ABA92A688;
 Mon,  6 Jul 2015 16:07:22 +0000 (UTC)
 (envelope-from pkelsey@FreeBSD.org)
Received: from repo.freebsd.org (repo.freebsd.org
 [IPv6:2001:1900:2254:2068::e6a:0])
 (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
 (Client did not present a certificate)
 by mx1.freebsd.org (Postfix) with ESMTPS id 9B6BF12F3;
 Mon,  6 Jul 2015 16:07:22 +0000 (UTC)
 (envelope-from pkelsey@FreeBSD.org)
Received: from repo.freebsd.org ([127.0.1.70])
 by repo.freebsd.org (8.14.9/8.14.9) with ESMTP id t66G7M6s037819;
 Mon, 6 Jul 2015 16:07:22 GMT (envelope-from pkelsey@FreeBSD.org)
Received: (from pkelsey@localhost)
 by repo.freebsd.org (8.14.9/8.14.9/Submit) id t66G7M72037818;
 Mon, 6 Jul 2015 16:07:22 GMT (envelope-from pkelsey@FreeBSD.org)
Message-Id: <201507061607.t66G7M72037818@repo.freebsd.org>
X-Authentication-Warning: repo.freebsd.org: pkelsey set sender to
 pkelsey@FreeBSD.org using -f
From: Patrick Kelsey <pkelsey@FreeBSD.org>
Date: Mon, 6 Jul 2015 16:07:22 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
 svn-src-head@freebsd.org
Subject: svn commit: r285208 - head/sys/kern
X-SVN-Group: head
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
X-BeenThere: svn-src-head@freebsd.org
X-Mailman-Version: 2.1.20
Precedence: list
List-Id: SVN commit messages for the src tree for head/-current
 <svn-src-head.freebsd.org>
List-Unsubscribe: <http://lists.freebsd.org/mailman/options/svn-src-head>,
 <mailto:svn-src-head-request@freebsd.org?subject=unsubscribe>
List-Archive: <http://lists.freebsd.org/pipermail/svn-src-head/>
List-Post: <mailto:svn-src-head@freebsd.org>
List-Help: <mailto:svn-src-head-request@freebsd.org?subject=help>
List-Subscribe: <http://lists.freebsd.org/mailman/listinfo/svn-src-head>,
 <mailto:svn-src-head-request@freebsd.org?subject=subscribe>
X-List-Received-Date: Mon, 06 Jul 2015 16:07:22 -0000

Author: pkelsey
Date: Mon Jul  6 16:07:21 2015
New Revision: 285208
URL: https://svnweb.freebsd.org/changeset/base/285208

Log:
  Don't acquire sysctlmemlock in userland_sysctl() when the old value
  pointer is NULL, as in that case there are no userland pages that
  could potentially be wired.  It is common for old to be NULL and
  oldlenp to be non-NULL in calls to userland_sysctl(), as this is used
  to probe for the length of a variable-length sysctl entry before
  retrieving a value.  Note that it is typical for such calls to be made
  with an uninitialized value in *oldlenp, so sysctlmemlock was
  essentially being acquired at random (depending on the uninitialized
  value in *oldlenp being > PAGE_SIZE or not) for these calls prior to
  this patch.
  
  Differential Revision: https://reviews.freebsd.org/D2987
  Reviewed by: mjg, kib
  Approved by: jmallett (mentor)
  MFC after: 1 month

Modified:
  head/sys/kern/kern_sysctl.c

Modified: head/sys/kern/kern_sysctl.c
==============================================================================
--- head/sys/kern/kern_sysctl.c	Mon Jul  6 14:09:00 2015	(r285207)
+++ head/sys/kern/kern_sysctl.c	Mon Jul  6 16:07:21 2015	(r285208)
@@ -1784,7 +1784,7 @@ userland_sysctl(struct thread *td, int *
 		ktrsysctl(name, namelen);
 #endif
 
-	if (req.oldlen > PAGE_SIZE) {
+	if (req.oldptr && req.oldlen > PAGE_SIZE) {
 		memlocked = 1;
 		sx_xlock(&sysctlmemlock);
 	} else