From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Theodore Ts'o" Subject: Re: [PATCH v2 5/5] fscrypt: fix race where ->lookup() marks plaintext dentry as ciphertext Date: Wed, 17 Apr 2019 10:24:35 -0400 Message-ID: <20190417142435.GE4686@mit.edu> References: <20190320183913.12686-1-ebiggers@kernel.org> <20190320183913.12686-6-ebiggers@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <20190320183913.12686-6-ebiggers@kernel.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net To: Eric Biggers Cc: linux-unionfs@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-fscrypt@vger.kernel.org, linux-mtd@lists.infradead.org, Sarthak Kukreti , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org List-Id: linux-unionfs@vger.kernel.org On Wed, Mar 20, 2019 at 11:39:13AM -0700, Eric Biggers wrote: > From: Eric Biggers > > ->lookup() in an encrypted directory begins as follows: > > 1. fscrypt_prepare_lookup(): > a. Try to load the directory's encryption key. > b. If the key is unavailable, mark the dentry as a ciphertext name > via d_flags. > 2. fscrypt_setup_filename(): > a. Try to load the directory's encryption key. > b. If the key is available, encrypt the name (treated as a plaintext > name) to get the on-disk name. Otherwise decode the name > (treated as a ciphertext name) to get the on-disk name. > > But if the key is concurrently added, it may be found at (2a) but not at > (1a). In this case, the dentry will be wrongly marked as a ciphertext > name even though it was actually treated as plaintext. > > This will cause the dentry to be wrongly invalidated on the next lookup, > potentially causing problems. For example, if the racy ->lookup() was > part of sys_mount(), then the new mount will be detached when anything > tries to access it. This is despite the mountpoint having a plaintext > path, which should remain valid now that the key was added. > > Of course, this is only possible if there's a userspace race. Still, > the additional kernel-side race is confusing and unexpected. > > Close the kernel-side race by changing fscrypt_prepare_lookup() to also > set the on-disk filename (step 2b), consistent with the d_flags update. > > Fixes: 28b4c263961c ("ext4 crypto: revalidate dentry after adding or removing the key") > Signed-off-by: Eric Biggers Looks good, applied. - Ted From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Wed, 17 Apr 2019 10:24:35 -0400 From: "Theodore Ts'o" Subject: Re: [PATCH v2 5/5] fscrypt: fix race where ->lookup() marks plaintext dentry as ciphertext Message-ID: <20190417142435.GE4686@mit.edu> References: <20190320183913.12686-1-ebiggers@kernel.org> <20190320183913.12686-6-ebiggers@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190320183913.12686-6-ebiggers@kernel.org> To: Eric Biggers Cc: linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-unionfs@vger.kernel.org, Sarthak Kukreti , Gao Xiang List-ID: On Wed, Mar 20, 2019 at 11:39:13AM -0700, Eric Biggers wrote: > From: Eric Biggers > > ->lookup() in an encrypted directory begins as follows: > > 1. fscrypt_prepare_lookup(): > a. Try to load the directory's encryption key. > b. If the key is unavailable, mark the dentry as a ciphertext name > via d_flags. > 2. fscrypt_setup_filename(): > a. Try to load the directory's encryption key. > b. If the key is available, encrypt the name (treated as a plaintext > name) to get the on-disk name. Otherwise decode the name > (treated as a ciphertext name) to get the on-disk name. > > But if the key is concurrently added, it may be found at (2a) but not at > (1a). In this case, the dentry will be wrongly marked as a ciphertext > name even though it was actually treated as plaintext. > > This will cause the dentry to be wrongly invalidated on the next lookup, > potentially causing problems. For example, if the racy ->lookup() was > part of sys_mount(), then the new mount will be detached when anything > tries to access it. This is despite the mountpoint having a plaintext > path, which should remain valid now that the key was added. > > Of course, this is only possible if there's a userspace race. Still, > the additional kernel-side race is confusing and unexpected. > > Close the kernel-side race by changing fscrypt_prepare_lookup() to also > set the on-disk filename (step 2b), consistent with the d_flags update. > > Fixes: 28b4c263961c ("ext4 crypto: revalidate dentry after adding or removing the key") > Signed-off-by: Eric Biggers Looks good, applied. - Ted 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=-5.5 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,USER_AGENT_MUTT 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 CE132C282DA for ; Wed, 17 Apr 2019 14:24:58 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9C01C20872 for ; Wed, 17 Apr 2019 14:24:58 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="HlApjCyt" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9C01C20872 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=mit.edu Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=7Y3+JZh2N97MWxMT7NJJ6zcegGTRxSN/Z47wGKFWMpw=; b=HlApjCytC+QsY4 RaXv8kHgUylh96rb0CDhciS+hh6raOw2WRz9rsrkdTMw/IbLR+vlUCyOQLwE4T3OoJLFF5I5GF1Sh +GkEb/53BFb6KoZQ/U8RIDL9LIMEq8WzK+JRw2Lk/Hu3OG7ZRJy+7gEaFcLOt/djKDi66q+qeKa2H AMCG0z7i93yyRuXRcBRALH34ePSiRjB5oy8KQKyLR7c2zhsIk/yKV6LU7Drbi0vINrupj/wXkHKEW pG2alFlSjj/DEOvUjG2fTU0lCsRmnILsEC/1iBU23YW/ZFwxAzZx2rAzIJfh3KOpDOKDcOtTty67Y IwRfp8xePdl5Yl4r8A2g==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1hGlUd-0001Lg-Qz; Wed, 17 Apr 2019 14:24:55 +0000 Received: from outgoing-auth-1.mit.edu ([18.9.28.11] helo=outgoing.mit.edu) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1hGlUX-0001Ga-4X for linux-mtd@lists.infradead.org; Wed, 17 Apr 2019 14:24:54 +0000 Received: from callcc.thunk.org (guestnat-104-133-0-109.corp.google.com [104.133.0.109] (may be forged)) (authenticated bits=0) (User authenticated as tytso@ATHENA.MIT.EDU) by outgoing.mit.edu (8.14.7/8.12.4) with ESMTP id x3HEOawa011053 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 17 Apr 2019 10:24:36 -0400 Received: by callcc.thunk.org (Postfix, from userid 15806) id E7C39420497; Wed, 17 Apr 2019 10:24:35 -0400 (EDT) Date: Wed, 17 Apr 2019 10:24:35 -0400 From: "Theodore Ts'o" To: Eric Biggers Subject: Re: [PATCH v2 5/5] fscrypt: fix race where ->lookup() marks plaintext dentry as ciphertext Message-ID: <20190417142435.GE4686@mit.edu> References: <20190320183913.12686-1-ebiggers@kernel.org> <20190320183913.12686-6-ebiggers@kernel.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190320183913.12686-6-ebiggers@kernel.org> User-Agent: Mutt/1.10.1 (2018-07-13) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190417_072449_648590_40FBFBA0 X-CRM114-Status: GOOD ( 13.05 ) X-BeenThere: linux-mtd@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: Linux MTD discussion mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Gao Xiang , linux-unionfs@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-fscrypt@vger.kernel.org, linux-mtd@lists.infradead.org, Sarthak Kukreti , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-mtd" Errors-To: linux-mtd-bounces+linux-mtd=archiver.kernel.org@lists.infradead.org On Wed, Mar 20, 2019 at 11:39:13AM -0700, Eric Biggers wrote: > From: Eric Biggers > > ->lookup() in an encrypted directory begins as follows: > > 1. fscrypt_prepare_lookup(): > a. Try to load the directory's encryption key. > b. If the key is unavailable, mark the dentry as a ciphertext name > via d_flags. > 2. fscrypt_setup_filename(): > a. Try to load the directory's encryption key. > b. If the key is available, encrypt the name (treated as a plaintext > name) to get the on-disk name. Otherwise decode the name > (treated as a ciphertext name) to get the on-disk name. > > But if the key is concurrently added, it may be found at (2a) but not at > (1a). In this case, the dentry will be wrongly marked as a ciphertext > name even though it was actually treated as plaintext. > > This will cause the dentry to be wrongly invalidated on the next lookup, > potentially causing problems. For example, if the racy ->lookup() was > part of sys_mount(), then the new mount will be detached when anything > tries to access it. This is despite the mountpoint having a plaintext > path, which should remain valid now that the key was added. > > Of course, this is only possible if there's a userspace race. Still, > the additional kernel-side race is confusing and unexpected. > > Close the kernel-side race by changing fscrypt_prepare_lookup() to also > set the on-disk filename (step 2b), consistent with the d_flags update. > > Fixes: 28b4c263961c ("ext4 crypto: revalidate dentry after adding or removing the key") > Signed-off-by: Eric Biggers Looks good, applied. - Ted ______________________________________________________ Linux MTD discussion mailing list http://lists.infradead.org/mailman/listinfo/linux-mtd/