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=-6.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT 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 02349C4360C for ; Sun, 6 Oct 2019 17:39:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CFB902133F for ; Sun, 6 Oct 2019 17:39:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570383550; bh=mQyM+MYzJfX0sMNye8DCPt5zXmK09F28LgbBWbDWYCw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=zyLjs+W4XcCufGkqbhZaCHdy7iAE4Xpgu/I8BYD5GaqDuCl1CEXu0OX8wAVCIfg5A PHVToxCRopM+DcT+CQ+CStXNxCARTr2zbYDftdlXo7rZSxKgD2GXkqc8AiYipz2S7t Oix8dPYuwAoehx8g9XopQM3KB1qDOU2gUszq08QY= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729853AbfJFRjK (ORCPT ); Sun, 6 Oct 2019 13:39:10 -0400 Received: from mail.kernel.org ([198.145.29.99]:38566 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729767AbfJFRjH (ORCPT ); Sun, 6 Oct 2019 13:39:07 -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 BADE4222BE; Sun, 6 Oct 2019 17:39:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1570383546; bh=mQyM+MYzJfX0sMNye8DCPt5zXmK09F28LgbBWbDWYCw=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=JUiZ5cgOTjDAR/aAnvCPEBk+pdx+0uGQ6KJnWH0PHYB5ltx80IBEn7G3BhGAm2XNS PX41yGr/108zRWPmd0xDdI7H1WlgmFKwNJV3l3zAHwF1Ywislk0Y2xPjy6YBQ/GPr3 3caKbNizFEG8EFw3cKZgZcvmE6rJ1OAs8XbrFDA4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, syzbot+7d6a57304857423318a5@syzkaller.appspotmail.com, David Howells , Miklos Szeredi , Eric Biggers , Al Viro Subject: [PATCH 5.2 137/137] vfs: set fs_context::user_ns for reconfigure Date: Sun, 6 Oct 2019 19:22:01 +0200 Message-Id: <20191006171220.808492952@linuxfoundation.org> X-Mailer: git-send-email 2.23.0 In-Reply-To: <20191006171209.403038733@linuxfoundation.org> References: <20191006171209.403038733@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: Eric Biggers commit 1dd9bc08cf1420d466dd8dcfcc233777e61ca5d2 upstream. fs_context::user_ns is used by fuse_parse_param(), even during remount, so it needs to be set to the existing value for reconfigure. Reproducer: #include #include int main() { char opts[128]; int fd = open("/dev/fuse", O_RDWR); sprintf(opts, "fd=%d,rootmode=040000,user_id=0,group_id=0", fd); mkdir("mnt", 0777); mount("foo", "mnt", "fuse.foo", 0, opts); mount("foo", "mnt", "fuse.foo", MS_REMOUNT, opts); } Crash: BUG: kernel NULL pointer dereference, address: 0000000000000000 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] SMP CPU: 0 PID: 129 Comm: syz_make_kuid Not tainted 5.3.0-rc5-next-20190821 #3 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-20181126_142135-anatol 04/01/2014 RIP: 0010:map_id_range_down+0xb/0xc0 kernel/user_namespace.c:291 [...] Call Trace: map_id_down kernel/user_namespace.c:312 [inline] make_kuid+0xe/0x10 kernel/user_namespace.c:389 fuse_parse_param+0x116/0x210 fs/fuse/inode.c:523 vfs_parse_fs_param+0xdb/0x1b0 fs/fs_context.c:145 vfs_parse_fs_string+0x6a/0xa0 fs/fs_context.c:188 generic_parse_monolithic+0x85/0xc0 fs/fs_context.c:228 parse_monolithic_mount_data+0x1b/0x20 fs/fs_context.c:708 do_remount fs/namespace.c:2525 [inline] do_mount+0x39a/0xa60 fs/namespace.c:3107 ksys_mount+0x7d/0xd0 fs/namespace.c:3325 __do_sys_mount fs/namespace.c:3339 [inline] __se_sys_mount fs/namespace.c:3336 [inline] __x64_sys_mount+0x20/0x30 fs/namespace.c:3336 do_syscall_64+0x4a/0x1a0 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe Reported-by: syzbot+7d6a57304857423318a5@syzkaller.appspotmail.com Fixes: 408cbe695350 ("vfs: Convert fuse to use the new mount API") Cc: David Howells Cc: Miklos Szeredi Signed-off-by: Eric Biggers Reviewed-by: David Howells Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman --- fs/fs_context.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) --- a/fs/fs_context.c +++ b/fs/fs_context.c @@ -279,10 +279,8 @@ static struct fs_context *alloc_fs_conte fc->user_ns = get_user_ns(reference->d_sb->s_user_ns); break; case FS_CONTEXT_FOR_RECONFIGURE: - /* We don't pin any namespaces as the superblock's - * subscriptions cannot be changed at this point. - */ atomic_inc(&reference->d_sb->s_active); + fc->user_ns = get_user_ns(reference->d_sb->s_user_ns); fc->root = dget(reference); break; }