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=-11.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, MENTIONS_GIT_HOSTING,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_GIT autolearn=unavailable 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 EB3FBC49ED7 for ; Thu, 19 Sep 2019 22:11:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B5383218AF for ; Thu, 19 Sep 2019 22:11:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568931084; bh=+BPb9aFqpMEOx8qFpFHPVr0Dux9gRUGsNun4XS+W0Ds=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=rJU5bN1mxO4r4M3+VJe9Kv2SojSy5msjy2u2+DNzRjCkGF0LqKYUG+awPDaX+1F0b 6m191ZLcSIDrHXGrKyI44u3iwFzw1vBFfxZCBmCDqAJNSU7icZa0pNgIooopC+Jdlr OWjPrD5TOyDJnuoyMbLTyG6X0K/S56pANLDjGiN0= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2393583AbfISWLX (ORCPT ); Thu, 19 Sep 2019 18:11:23 -0400 Received: from mail.kernel.org ([198.145.29.99]:49980 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2393561AbfISWLU (ORCPT ); Thu, 19 Sep 2019 18:11:20 -0400 Received: from localhost (83-86-89-107.cable.dynamic.v4.ziggo.nl [83.86.89.107]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 14A7B21920; Thu, 19 Sep 2019 22:11:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1568931079; bh=+BPb9aFqpMEOx8qFpFHPVr0Dux9gRUGsNun4XS+W0Ds=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hyh5cX7fSgMp7nOGwgFbCWNk9qWbaFYSQDgvbp7K3cxycotMrr3eTiAoQqEOPKALI 3dchvybt3kidxuCG6G7UPfs4Fx+Q8VJZt5OfyrhMBx+ofmaIrZUhDE+BRQDuP9HCvl 6weumTbc+RTNISVFzB2ChSZqITCUGvOTo3sJCngA= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Amir Goldstein , Colin Walters , Miklos Szeredi Subject: [PATCH 5.2 121/124] ovl: fix regression caused by overlapping layers detection Date: Fri, 20 Sep 2019 00:03:29 +0200 Message-Id: <20190919214823.578495152@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20190919214819.198419517@linuxfoundation.org> References: <20190919214819.198419517@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Amir Goldstein commit 0be0bfd2de9dfdd2098a9c5b14bdd8f739c9165d upstream. Once upon a time, commit 2cac0c00a6cd ("ovl: get exclusive ownership on upper/work dirs") in v4.13 added some sanity checks on overlayfs layers. This change caused a docker regression. The root cause was mount leaks by docker, which as far as I know, still exist. To mitigate the regression, commit 85fdee1eef1a ("ovl: fix regression caused by exclusive upper/work dir protection") in v4.14 turned the mount errors into warnings for the default index=off configuration. Recently, commit 146d62e5a586 ("ovl: detect overlapping layers") in v5.2, re-introduced exclusive upper/work dir checks regardless of index=off configuration. This changes the status quo and mount leak related bug reports have started to re-surface. Restore the status quo to fix the regressions. To clarify, index=off does NOT relax overlapping layers check for this ovelayfs mount. index=off only relaxes exclusive upper/work dir checks with another overlayfs mount. To cover the part of overlapping layers detection that used the exclusive upper/work dir checks to detect overlap with self upper/work dir, add a trap also on the work base dir. Link: https://github.com/moby/moby/issues/34672 Link: https://lore.kernel.org/linux-fsdevel/20171006121405.GA32700@veci.piliscsaba.szeredi.hu/ Link: https://github.com/containers/libpod/issues/3540 Fixes: 146d62e5a586 ("ovl: detect overlapping layers") Cc: # v4.19+ Signed-off-by: Amir Goldstein Tested-by: Colin Walters Signed-off-by: Miklos Szeredi Signed-off-by: Greg Kroah-Hartman --- Documentation/filesystems/overlayfs.txt | 2 fs/overlayfs/ovl_entry.h | 1 fs/overlayfs/super.c | 73 ++++++++++++++++++++------------ 3 files changed, 49 insertions(+), 27 deletions(-) --- a/Documentation/filesystems/overlayfs.txt +++ b/Documentation/filesystems/overlayfs.txt @@ -302,7 +302,7 @@ beneath or above the path of another ove Using an upper layer path and/or a workdir path that are already used by another overlay mount is not allowed and may fail with EBUSY. Using -partially overlapping paths is not allowed but will not fail with EBUSY. +partially overlapping paths is not allowed and may fail with EBUSY. If files are accessed from two overlayfs mounts which share or overlap the upper layer and/or workdir path the behavior of the overlay is undefined, though it will not result in a crash or deadlock. --- a/fs/overlayfs/ovl_entry.h +++ b/fs/overlayfs/ovl_entry.h @@ -66,6 +66,7 @@ struct ovl_fs { bool workdir_locked; /* Traps in ovl inode cache */ struct inode *upperdir_trap; + struct inode *workbasedir_trap; struct inode *workdir_trap; struct inode *indexdir_trap; /* Inode numbers in all layers do not use the high xino_bits */ --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -212,6 +212,7 @@ static void ovl_free_fs(struct ovl_fs *o { unsigned i; + iput(ofs->workbasedir_trap); iput(ofs->indexdir_trap); iput(ofs->workdir_trap); iput(ofs->upperdir_trap); @@ -1003,6 +1004,25 @@ static int ovl_setup_trap(struct super_b return 0; } +/* + * Determine how we treat concurrent use of upperdir/workdir based on the + * index feature. This is papering over mount leaks of container runtimes, + * for example, an old overlay mount is leaked and now its upperdir is + * attempted to be used as a lower layer in a new overlay mount. + */ +static int ovl_report_in_use(struct ovl_fs *ofs, const char *name) +{ + if (ofs->config.index) { + pr_err("overlayfs: %s is in-use as upperdir/workdir of another mount, mount with '-o index=off' to override exclusive upperdir protection.\n", + name); + return -EBUSY; + } else { + pr_warn("overlayfs: %s is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.\n", + name); + return 0; + } +} + static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs, struct path *upperpath) { @@ -1040,14 +1060,12 @@ static int ovl_get_upper(struct super_bl upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME); ofs->upper_mnt = upper_mnt; - err = -EBUSY; if (ovl_inuse_trylock(ofs->upper_mnt->mnt_root)) { ofs->upperdir_locked = true; - } else if (ofs->config.index) { - pr_err("overlayfs: upperdir is in-use by another mount, mount with '-o index=off' to override exclusive upperdir protection.\n"); - goto out; } else { - pr_warn("overlayfs: upperdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n"); + err = ovl_report_in_use(ofs, "upperdir"); + if (err) + goto out; } err = 0; @@ -1157,16 +1175,19 @@ static int ovl_get_workdir(struct super_ ofs->workbasedir = dget(workpath.dentry); - err = -EBUSY; if (ovl_inuse_trylock(ofs->workbasedir)) { ofs->workdir_locked = true; - } else if (ofs->config.index) { - pr_err("overlayfs: workdir is in-use by another mount, mount with '-o index=off' to override exclusive workdir protection.\n"); - goto out; } else { - pr_warn("overlayfs: workdir is in-use by another mount, accessing files from both mounts will result in undefined behavior.\n"); + err = ovl_report_in_use(ofs, "workdir"); + if (err) + goto out; } + err = ovl_setup_trap(sb, ofs->workbasedir, &ofs->workbasedir_trap, + "workdir"); + if (err) + goto out; + err = ovl_make_workdir(sb, ofs, &workpath); out: @@ -1313,16 +1334,16 @@ static int ovl_get_lower_layers(struct s if (err < 0) goto out; - err = -EBUSY; - if (ovl_is_inuse(stack[i].dentry)) { - pr_err("overlayfs: lowerdir is in-use as upperdir/workdir\n"); - goto out; - } - err = ovl_setup_trap(sb, stack[i].dentry, &trap, "lowerdir"); if (err) goto out; + if (ovl_is_inuse(stack[i].dentry)) { + err = ovl_report_in_use(ofs, "lowerdir"); + if (err) + goto out; + } + mnt = clone_private_mount(&stack[i]); err = PTR_ERR(mnt); if (IS_ERR(mnt)) { @@ -1469,8 +1490,8 @@ out_err: * - another layer of this overlayfs instance * - upper/work dir of any overlayfs instance */ -static int ovl_check_layer(struct super_block *sb, struct dentry *dentry, - const char *name) +static int ovl_check_layer(struct super_block *sb, struct ovl_fs *ofs, + struct dentry *dentry, const char *name) { struct dentry *next = dentry, *parent; int err = 0; @@ -1482,13 +1503,11 @@ static int ovl_check_layer(struct super_ /* Walk back ancestors to root (inclusive) looking for traps */ while (!err && parent != next) { - if (ovl_is_inuse(parent)) { - err = -EBUSY; - pr_err("overlayfs: %s path overlapping in-use upperdir/workdir\n", - name); - } else if (ovl_lookup_trap_inode(sb, parent)) { + if (ovl_lookup_trap_inode(sb, parent)) { err = -ELOOP; pr_err("overlayfs: overlapping %s path\n", name); + } else if (ovl_is_inuse(parent)) { + err = ovl_report_in_use(ofs, name); } next = parent; parent = dget_parent(next); @@ -1509,7 +1528,8 @@ static int ovl_check_overlapping_layers( int i, err; if (ofs->upper_mnt) { - err = ovl_check_layer(sb, ofs->upper_mnt->mnt_root, "upperdir"); + err = ovl_check_layer(sb, ofs, ofs->upper_mnt->mnt_root, + "upperdir"); if (err) return err; @@ -1520,13 +1540,14 @@ static int ovl_check_overlapping_layers( * workbasedir. In that case, we already have their traps in * inode cache and we will catch that case on lookup. */ - err = ovl_check_layer(sb, ofs->workbasedir, "workdir"); + err = ovl_check_layer(sb, ofs, ofs->workbasedir, "workdir"); if (err) return err; } for (i = 0; i < ofs->numlower; i++) { - err = ovl_check_layer(sb, ofs->lower_layers[i].mnt->mnt_root, + err = ovl_check_layer(sb, ofs, + ofs->lower_layers[i].mnt->mnt_root, "lowerdir"); if (err) return err;