From owner-svn-src-head@freebsd.org Tue Apr 12 19:11:15 2016 Return-Path: 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 A526AB0D5F7; Tue, 12 Apr 2016 19:11:15 +0000 (UTC) (envelope-from asomers@FreeBSD.org) Received: from repo.freebsd.org (repo.freebsd.org [IPv6:2610:1c1:1:6068::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 5EEE8104E; Tue, 12 Apr 2016 19:11:15 +0000 (UTC) (envelope-from asomers@FreeBSD.org) Received: from repo.freebsd.org ([127.0.1.37]) by repo.freebsd.org (8.15.2/8.15.2) with ESMTP id u3CJBEel006613; Tue, 12 Apr 2016 19:11:14 GMT (envelope-from asomers@FreeBSD.org) Received: (from asomers@localhost) by repo.freebsd.org (8.15.2/8.15.2/Submit) id u3CJBEBm006612; Tue, 12 Apr 2016 19:11:14 GMT (envelope-from asomers@FreeBSD.org) Message-Id: <201604121911.u3CJBEBm006612@repo.freebsd.org> X-Authentication-Warning: repo.freebsd.org: asomers set sender to asomers@FreeBSD.org using -f From: Alan Somers Date: Tue, 12 Apr 2016 19:11:14 +0000 (UTC) To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r297868 - head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs 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: 2.1.21 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 12 Apr 2016 19:11:15 -0000 Author: asomers Date: Tue Apr 12 19:11:14 2016 New Revision: 297868 URL: https://svnweb.freebsd.org/changeset/base/297868 Log: Fix rare double free in vdev_geom_attrchanged sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c Don't drop the g_topology_lock before freeing old_physpath. That opens up a race where one thread can call vdev_geom_attrchanged, set old_physpath, drop the g_topology_lock, then block trying to acquire the SCL_STATE lock. Then another thread can come into vdev_geom_attrchanged, set old_physpath to the same value, and proceed to free it. When the first thread resumes, it will free the same location. It turns out that the SCL_STATE lock isn't needed. It was originally added by gibbs to protect vd->vdev_physpath while updating the same. However, the update process subsequently was switched to an atomic operation (a pointer swap). Now, there is no need for the SCL_STATE lock, and hence no need to drop the g_topology_lock. Reviewed by: delphij MFC after: 4 weeks Sponsored by: Spectra Logic Corp Differential Revision: https://reviews.freebsd.org/D5413 Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c Modified: head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c ============================================================================== --- head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c Tue Apr 12 18:50:37 2016 (r297867) +++ head/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c Tue Apr 12 19:11:14 2016 (r297868) @@ -115,27 +115,14 @@ vdev_geom_attrchanged(struct g_consumer if (error == 0) { char *old_physpath; + /* g_topology lock ensures that vdev has not been closed */ + g_topology_assert(); old_physpath = vd->vdev_physpath; vd->vdev_physpath = spa_strdup(physpath); spa_async_request(spa, SPA_ASYNC_CONFIG_UPDATE); - if (old_physpath != NULL) { - int held_lock; - - held_lock = spa_config_held(spa, SCL_STATE, RW_WRITER); - if (held_lock == 0) { - g_topology_unlock(); - spa_config_enter(spa, SCL_STATE, FTAG, - RW_WRITER); - } - + if (old_physpath != NULL) spa_strfree(old_physpath); - - if (held_lock == 0) { - spa_config_exit(spa, SCL_STATE, FTAG); - g_topology_lock(); - } - } } g_free(physpath); }