From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f195.google.com ([209.85.192.195]:33999 "EHLO mail-pf0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752456AbdFMXtJ (ORCPT ); Tue, 13 Jun 2017 19:49:09 -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 2/3] f2fs: require key for truncate(2) of encrypted file Date: Tue, 13 Jun 2017 16:47:54 -0700 Message-Id: <20170613234755.111167-3-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/f2fs/file.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c index 61af721329fa..be0b32bd1297 100644 --- a/fs/f2fs/file.c +++ b/fs/f2fs/file.c @@ -682,9 +682,13 @@ int f2fs_setattr(struct dentry *dentry, struct iattr *attr) return err; if (attr->ia_valid & ATTR_SIZE) { - if (f2fs_encrypted_inode(inode) && - fscrypt_get_encryption_info(inode)) - return -EACCES; + if (f2fs_encrypted_inode(inode)) { + err = fscrypt_get_encryption_info(inode); + if (err) + return err; + if (!fscrypt_has_encryption_key(inode)) + return -ENOKEY; + } if (attr->ia_size <= i_size_read(inode)) { truncate_setsize(inode, attr->ia_size); -- 2.13.1.508.gb3defc5cc-goog