From patchwork Sun Oct 8 21:55:30 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Theodore Ts'o X-Patchwork-Id: 823042 Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=linux-ext4-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dkim=fail reason="signature verification failed" (1024-bit key; unprotected) header.d=thunk.org header.i=@thunk.org header.b="jKDneOOA"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3y9HHW0CNGz9t3p for ; Mon, 9 Oct 2017 08:55:35 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751545AbdJHVzd (ORCPT ); Sun, 8 Oct 2017 17:55:33 -0400 Received: from imap.thunk.org ([74.207.234.97]:49886 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751214AbdJHVzc (ORCPT ); Sun, 8 Oct 2017 17:55:32 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=thunk.org; s=ef5046eb; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID: Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=GDs4tR55HAxDP069PhfrxFJ9O7i/9JqUQvgUo9fkP2g=; b=jKDneOOA0DyaDYvE/Ojgidd6Z3 1UKuTaWdPFoCbmkSWNsfnsXFEuj45phwloW3XLu3tYUpk6XvgtcH0hBRDKd/D49P7F/pq2/RBCU4z E2uaxG2+bOxjia20psgQ0QIt7MGi/FwW0M34hjgaSNI/tySx1TMpgnNduoNBUTUn6r30=; Received: from root (helo=callcc.thunk.org) by imap.thunk.org with local-esmtp (Exim 4.89) (envelope-from ) id 1e1JXn-00026O-CA; Sun, 08 Oct 2017 21:55:31 +0000 Received: by callcc.thunk.org (Postfix, from userid 15806) id 39882C011A6; Sun, 8 Oct 2017 17:55:30 -0400 (EDT) Date: Sun, 8 Oct 2017 17:55:30 -0400 From: Theodore Ts'o To: Eric Biggers Cc: stable@vger.kernel.org, linux-ext4@vger.kernel.org Subject: [FOR STABLE 4.1 -v2] ext4 crypto: don't regenerate the per-inode encryption key unnecessarily Message-ID: <20171008215530.hnty5a7v6dsip45e@thunk.org> References: <20171008180953.rpnxvpggqggc334m@thunk.org> <20171008191749.GA26458@zzz.localdomain> <20171008203449.ys4sg5xztbzxx6ik@thunk.org> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20171008203449.ys4sg5xztbzxx6ik@thunk.org> User-Agent: NeoMutt/20170609 (1.8.3) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on imap.thunk.org); SAEximRunCond expanded to false Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org From 8912051518ca75a94670652722c72e412eafe674 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Sun, 8 Oct 2017 13:32:21 -0400 Subject: [PATCH] ext4 crypto: don't regenerate the per-inode encryption key unnecessarily [ Relevant upstream commit: 1b53cf9815bb4744958d41f3795d5d5a1d365e2d ] This fixes the same problem as upstream commit 1b53cf9815bb: "fscrypt: remove broken support for detecting keyring key revocation". Specifically, key revocations racing with readpage operations will cause the kernel to crash and burn with a BUG_ON or a NULL pointer dereference in a block I/O callback stemming from an ext4_readpage() operation. This fix is needed to fix prevent xfstests test runs from crashing while running the generic/421 test. The root cause is different in the 4.1 kernel, however, since the 4.1's encryption handling is so _primitive_ compared to later kernels. The code isn't actually explicitly checking for revoked keys. Instead, the code is neededly regenerating the per-file encryption key on every mmap() or open() or directory operation (in the case of a directory inode). Yelch! If the file is already opened and actively being read, and there is a racing open() after the user's master key has been revoked, there will be the same net effect as the problem fixed by upstream commit 1b53cf9815bb --- the per-file key will be marked as invalid and this will cause a BUG_ON. In the AOSP 3.18 and 4.4 android-common kernels, the more modern version of ext4 encryption have been backported, including a backport of upstream commit 1b53cf9815bb. This is a dozen plus commits, and isn't really suitable for the Upstream LTS kernel. So instead, this is the simplest bug which fixes the same high-level issue as the upstream commit, without dragging in all of the other non-bug fixes improvements to the ext4 encryption code found in newer kernels. Signed-off-by: Theodore Ts'o --- fs/ext4/crypto_key.c | 15 ++++++++++++--- fs/ext4/ext4.h | 1 + fs/ext4/super.c | 3 +++ 3 files changed, 16 insertions(+), 3 deletions(-) diff --git a/fs/ext4/crypto_key.c b/fs/ext4/crypto_key.c index 52170d0b7c40..4f9818719d61 100644 --- a/fs/ext4/crypto_key.c +++ b/fs/ext4/crypto_key.c @@ -99,9 +99,17 @@ int ext4_generate_encryption_key(struct inode *inode) struct ext4_encryption_context ctx; struct user_key_payload *ukp; struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); - int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION, - EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, - &ctx, sizeof(ctx)); + int res; + + mutex_lock(&ei->i_encryption_lock); + if (ext4_has_encryption_key(inode)) { + mutex_unlock(&ei->i_encryption_lock); + return 0; + } + + res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION, + EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, + &ctx, sizeof(ctx)); if (res != sizeof(ctx)) { if (res > 0) @@ -154,6 +162,7 @@ out: key_put(keyring_key); if (res < 0) crypt_key->mode = EXT4_ENCRYPTION_MODE_INVALID; + mutex_unlock(&ei->i_encryption_lock); return res; } diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index df67a6f8582a..01771ed4529d 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -989,6 +989,7 @@ struct ext4_inode_info { #ifdef CONFIG_EXT4_FS_ENCRYPTION /* Encryption params */ struct ext4_encryption_key i_encryption_key; + struct mutex i_encryption_lock; #endif }; diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 97aa8be40175..683eb88863dc 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -946,6 +946,9 @@ static void init_once(void *foo) init_rwsem(&ei->xattr_sem); init_rwsem(&ei->i_data_sem); init_rwsem(&ei->i_mmap_sem); +#ifdef CONFIG_EXT4_FS_ENCRYPTION + mutex_init(&ei->i_encryption_lock); +#endif inode_init_once(&ei->vfs_inode); }