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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 5E552C47083 for ; Fri, 4 Jun 2021 16:12:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4658D61405 for ; Fri, 4 Jun 2021 16:12:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231286AbhFDQOE convert rfc822-to-8bit (ORCPT ); Fri, 4 Jun 2021 12:14:04 -0400 Received: from us-smtp-delivery-44.mimecast.com ([207.211.30.44]:35044 "EHLO us-smtp-delivery-44.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230453AbhFDQOC (ORCPT ); Fri, 4 Jun 2021 12:14:02 -0400 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-177-_9AFksQQM9iDjBrWox_Xcg-1; Fri, 04 Jun 2021 12:12:14 -0400 X-MC-Unique: _9AFksQQM9iDjBrWox_Xcg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 80AF9801817; Fri, 4 Jun 2021 16:12:13 +0000 (UTC) Received: from bahia.lan (ovpn-112-232.ams2.redhat.com [10.36.112.232]) by smtp.corp.redhat.com (Postfix) with ESMTP id 15F3060CEC; Fri, 4 Jun 2021 16:12:11 +0000 (UTC) From: Greg Kurz To: Miklos Szeredi Cc: linux-kernel@vger.kernel.org, Max Reitz , linux-fsdevel@vger.kernel.org, virtio-fs@redhat.com, Vivek Goyal , Greg Kurz Subject: [PATCH v2 2/7] fuse: Fix crash if superblock of submount gets killed early Date: Fri, 4 Jun 2021 18:11:51 +0200 Message-Id: <20210604161156.408496-3-groug@kaod.org> In-Reply-To: <20210604161156.408496-1-groug@kaod.org> References: <20210604161156.408496-1-groug@kaod.org> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: kaod.org Content-Transfer-Encoding: 8BIT Content-Type: text/plain; charset=WINDOWS-1252 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org As soon as fuse_dentry_automount() does up_write(&sb->s_umount), the superblock can theoretically be killed. If this happens before the submount was added to the &fc->mounts list, fuse_mount_remove() later crashes in list_del_init() because it assumes the submount to be already there. Add the submount before dropping sb->s_umount to fix the inconsistency. It is okay to nest fc->killsb under sb->s_umount, we already do this on the ->kill_sb() path. Signed-off-by: Greg Kurz --- fs/fuse/dir.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 01559061cbfb..3fd1b71e546b 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -346,15 +346,15 @@ static struct vfsmount *fuse_dentry_automount(struct path *path) goto out_put_sb; } + down_write(&fc->killsb); + list_add_tail(&fm->fc_entry, &fc->mounts); + up_write(&fc->killsb); + sb->s_flags |= SB_ACTIVE; fsc->root = dget(sb->s_root); /* We are done configuring the superblock, so unlock it */ up_write(&sb->s_umount); - down_write(&fc->killsb); - list_add_tail(&fm->fc_entry, &fc->mounts); - up_write(&fc->killsb); - /* Create the submount */ mnt = vfs_create_mount(fsc); if (IS_ERR(mnt)) { -- 2.31.1