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,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 22409C3524D for ; Mon, 3 Feb 2020 16:23:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EAD042080D for ; Mon, 3 Feb 2020 16:23:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580746984; bh=WIITaM8Y9JTtZxsqHdkwulwYQlCcQWStSmIDcvjHjx8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=uoAXLG6U0vSJpmLeJBn2IKR0p3ho0/wAzblqAg/GR0zFpUw2Bhh7e4gUPazRshS/i Mo+6zcgW72ov9S0jucrV8h95rewIECERBShIbIJzd01bY7iV0x49Q7bm86IfQNBus4 JEzM+YnwPtBQuFkH7yCzVPdMoGdRN5bpMu4ESGqM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728887AbgBCQU3 (ORCPT ); Mon, 3 Feb 2020 11:20:29 -0500 Received: from mail.kernel.org ([198.145.29.99]:60306 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728541AbgBCQU3 (ORCPT ); Mon, 3 Feb 2020 11:20:29 -0500 Received: from localhost (unknown [104.132.45.99]) (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 14C2020838; Mon, 3 Feb 2020 16:20:27 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1580746828; bh=WIITaM8Y9JTtZxsqHdkwulwYQlCcQWStSmIDcvjHjx8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=I7cQsuirZzuefpx5IcjvaXgg43ZkxboIlwC8Z86g3Zy9FJLy9PvFJsuN9hXNeqdpi jnbMSkLI1iPIhrSEIDmXr7Hh0j+TxNj/yDX4kGEQkN0ik+AWRsmERkdNt3sjqSIWpt YP0UzkaEs2QKqXbBHabQABGOBWYkSmeQ1+40k9oo= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, "Rantala, Tommi T. (Nokia - FI/Espoo)" , syzbot+190005201ced78a74ad6@syzkaller.appspotmail.com, stable@kernel.org, Al Viro , Linus Torvalds Subject: [PATCH 4.4 23/53] vfs: fix do_last() regression Date: Mon, 3 Feb 2020 16:19:15 +0000 Message-Id: <20200203161907.289417636@linuxfoundation.org> X-Mailer: git-send-email 2.25.0 In-Reply-To: <20200203161902.714326084@linuxfoundation.org> References: <20200203161902.714326084@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Al Viro commit 6404674acd596de41fd3ad5f267b4525494a891a upstream. Brown paperbag time: fetching ->i_uid/->i_mode really should've been done from nd->inode. I even suggested that, but the reason for that has slipped through the cracks and I went for dir->d_inode instead - made for more "obvious" patch. Analysis: - at the entry into do_last() and all the way to step_into(): dir (aka nd->path.dentry) is known not to have been freed; so's nd->inode and it's equal to dir->d_inode unless we are already doomed to -ECHILD. inode of the file to get opened is not known. - after step_into(): inode of the file to get opened is known; dir might be pointing to freed memory/be negative/etc. - at the call of may_create_in_sticky(): guaranteed to be out of RCU mode; inode of the file to get opened is known and pinned; dir might be garbage. The last was the reason for the original patch. Except that at the do_last() entry we can be in RCU mode and it is possible that nd->path.dentry->d_inode has already changed under us. In that case we are going to fail with -ECHILD, but we need to be careful; nd->inode is pointing to valid struct inode and it's the same as nd->path.dentry->d_inode in "won't fail with -ECHILD" case, so we should use that. Reported-by: "Rantala, Tommi T. (Nokia - FI/Espoo)" Reported-by: syzbot+190005201ced78a74ad6@syzkaller.appspotmail.com Wearing-brown-paperbag: Al Viro Cc: stable@kernel.org Fixes: d0cb50185ae9 ("do_last(): fetch directory ->i_mode and ->i_uid before it's too late") Signed-off-by: Al Viro Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- fs/namei.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/fs/namei.c +++ b/fs/namei.c @@ -3060,8 +3060,8 @@ static int do_last(struct nameidata *nd, int *opened) { struct dentry *dir = nd->path.dentry; - kuid_t dir_uid = dir->d_inode->i_uid; - umode_t dir_mode = dir->d_inode->i_mode; + kuid_t dir_uid = nd->inode->i_uid; + umode_t dir_mode = nd->inode->i_mode; int open_flag = op->open_flag; bool will_truncate = (open_flag & O_TRUNC) != 0; bool got_write = false;