From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.linuxfoundation.org ([140.211.169.12]:51472 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753249AbeBUJjx (ORCPT ); Wed, 21 Feb 2018 04:39:53 -0500 Subject: Patch "vfs: don't do RCU lookup of empty pathnames" has been added to the 3.18-stable tree To: torvalds@linux-foundation.org, dvyukov@google.com, ebiggers3@gmail.com, gregkh@linuxfoundation.org, vegard.nossum@gmail.com, viro@zeniv.linux.org.uk Cc: , From: Date: Wed, 21 Feb 2018 10:39:54 +0100 Message-ID: <1519205994232179@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=ANSI_X3.4-1968 Content-Transfer-Encoding: 8bit Sender: stable-owner@vger.kernel.org List-ID: This is a note to let you know that I've just added the patch titled vfs: don't do RCU lookup of empty pathnames to the 3.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: vfs-don-t-do-rcu-lookup-of-empty-pathnames.patch and it can be found in the queue-3.18 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let know about it. >>From c0eb027e5aef70b71e5a38ee3e264dc0b497f343 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Sun, 2 Apr 2017 17:10:08 -0700 Subject: vfs: don't do RCU lookup of empty pathnames From: Linus Torvalds commit c0eb027e5aef70b71e5a38ee3e264dc0b497f343 upstream. Normal pathname lookup doesn't allow empty pathnames, but using AT_EMPTY_PATH (with name_to_handle_at() or fstatat(), for example) you can trigger an empty pathname lookup. And not only is the RCU lookup in that case entirely unnecessary (because we'll obviously immediately finalize the end result), it is actively wrong. Why? An empth path is a special case that will return the original 'dirfd' dentry - and that dentry may not actually be RCU-free'd, resulting in a potential use-after-free if we were to initialize the path lazily under the RCU read lock and depend on complete_walk() finalizing the dentry. Found by syzkaller and KASAN. Reported-by: Dmitry Vyukov Reported-by: Vegard Nossum Acked-by: Al Viro Signed-off-by: Linus Torvalds Cc: Eric Biggers Signed-off-by: Greg Kroah-Hartman --- fs/namei.c | 3 +++ 1 file changed, 3 insertions(+) --- a/fs/namei.c +++ b/fs/namei.c @@ -1851,6 +1851,9 @@ static int path_init(int dfd, const char { int retval = 0; + if (!*s) + flags &= ~LOOKUP_RCU; + nd->last_type = LAST_ROOT; /* if there are only slashes... */ nd->flags = flags | LOOKUP_JUMPED; nd->depth = 0; Patches currently in stable-queue which might be from torvalds@linux-foundation.org are queue-3.18/vfs-don-t-do-rcu-lookup-of-empty-pathnames.patch