From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A0220C4CEC9 for ; Fri, 20 Sep 2019 14:34:52 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7DB8F207E0 for ; Fri, 20 Sep 2019 14:34:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392137AbfITOev (ORCPT ); Fri, 20 Sep 2019 10:34:51 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:36232 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388188AbfITOZG (ORCPT ); Fri, 20 Sep 2019 10:25:06 -0400 Received: from [192.168.4.242] (helo=deadeye) by shadbolt.decadent.org.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1iBJqJ-0004y2-TZ; Fri, 20 Sep 2019 15:25:03 +0100 Received: from ben by deadeye with local (Exim 4.92.1) (envelope-from ) id 1iBJqG-0007x8-NO; Fri, 20 Sep 2019 15:25:00 +0100 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, Denis Kirjanov , "Bob Peterson" Date: Fri, 20 Sep 2019 15:23:35 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) X-Patchwork-Hint: ignore Subject: [PATCH 3.16 103/132] GFS2: don't set rgrp gl_object until it's inserted into rgrp tree In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.242 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.16.74-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Bob Peterson commit 36e4ad0316c017d5b271378ed9a1c9a4b77fab5f upstream. Before this patch, function read_rindex_entry would set a rgrp glock's gl_object pointer to itself before inserting the rgrp into the rgrp rbtree. The problem is: if another process was also reading the rgrp in, and had already inserted its newly created rgrp, then the second call to read_rindex_entry would overwrite that value, then return a bad return code to the caller. Later, other functions would reference the now-freed rgrp memory by way of gl_object. In some cases, that could result in gfs2_rgrp_brelse being called twice for the same rgrp: once for the failed attempt and once for the "real" rgrp release. Eventually the kernel would panic. There are also a number of other things that could go wrong when a kernel module is accessing freed storage. For example, this could result in rgrp corruption because the fake rgrp would point to a fake bitmap in memory too, causing gfs2_inplace_reserve to search some random memory for free blocks, and find some, since we were never setting rgd->rd_bits to NULL before freeing it. This patch fixes the problem by not setting gl_object until we have successfully inserted the rgrp into the rbtree. Also, it sets rd_bits to NULL as it frees them, which will ensure any accidental access to the wrong rgrp will result in a kernel panic rather than file system corruption, which is preferred. Signed-off-by: Bob Peterson [bwh: Backported to 3.16: adjust context] Signed-off-by: Ben Hutchings --- --- a/fs/gfs2/rgrp.c +++ b/fs/gfs2/rgrp.c @@ -731,6 +731,7 @@ void gfs2_clear_rgrpd(struct gfs2_sbd *s gfs2_free_clones(rgd); kfree(rgd->rd_bits); + rgd->rd_bits = NULL; return_all_reservations(rgd); kmem_cache_free(gfs2_rgrpd_cachep, rgd); } @@ -925,10 +926,6 @@ static int read_rindex_entry(struct gfs2 if (error) goto fail; - rgd->rd_gl->gl_object = rgd; - rgd->rd_gl->gl_vm.start = (rgd->rd_addr * bsize) & PAGE_CACHE_MASK; - rgd->rd_gl->gl_vm.end = PAGE_CACHE_ALIGN((rgd->rd_addr + - rgd->rd_length) * bsize) - 1; rgd->rd_rgl = (struct gfs2_rgrp_lvb *)rgd->rd_gl->gl_lksb.sb_lvbptr; rgd->rd_flags &= ~GFS2_RDF_UPTODATE; if (rgd->rd_data > sdp->sd_max_rg_data) @@ -936,14 +933,20 @@ static int read_rindex_entry(struct gfs2 spin_lock(&sdp->sd_rindex_spin); error = rgd_insert(rgd); spin_unlock(&sdp->sd_rindex_spin); - if (!error) + if (!error) { + rgd->rd_gl->gl_object = rgd; + rgd->rd_gl->gl_vm.start = (rgd->rd_addr * bsize) & PAGE_MASK; + rgd->rd_gl->gl_vm.end = PAGE_ALIGN((rgd->rd_addr + + rgd->rd_length) * bsize) - 1; return 0; + } error = 0; /* someone else read in the rgrp; free it and ignore it */ gfs2_glock_put(rgd->rd_gl); fail: kfree(rgd->rd_bits); + rgd->rd_bits = NULL; kmem_cache_free(gfs2_rgrpd_cachep, rgd); return error; }