From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f194.google.com ([209.85.192.194]:33982 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752456AbdFMXtH (ORCPT ); Tue, 13 Jun 2017 19:49:07 -0400 From: Eric Biggers To: linux-fscrypt@vger.kernel.org Cc: Theodore Ts'o , linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, Eric Biggers Subject: [PATCH 1/3] ext4: require key for truncate(2) of encrypted file Date: Tue, 13 Jun 2017 16:47:53 -0700 Message-Id: <20170613234755.111167-2-ebiggers3@gmail.com> In-Reply-To: <20170613234755.111167-1-ebiggers3@gmail.com> References: <20170613234755.111167-1-ebiggers3@gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: From: Eric Biggers Currently, filesystems allow truncate(2) on an encrypted file without the encryption key. However, it's impossible to correctly handle the case where the size being truncated to is not a multiple of the filesystem block size, because that would require decrypting the final block, zeroing the part beyond i_size, then encrypting the block. As other modifications to encrypted file contents are prohibited without the key, just prohibit truncate(2) as well, making it fail with ENOKEY. Signed-off-by: Eric Biggers --- fs/ext4/inode.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 5cf82d03968c..baf8630de6a5 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -5307,6 +5307,14 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr) loff_t oldsize = inode->i_size; int shrink = (attr->ia_size <= inode->i_size); + if (ext4_encrypted_inode(inode)) { + error = fscrypt_get_encryption_info(inode); + if (error) + return error; + if (!fscrypt_has_encryption_key(inode)) + return -ENOKEY; + } + if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) { struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); -- 2.13.1.508.gb3defc5cc-goog