From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Biggers Subject: [PATCH 3/3] ubifs: require key for truncate(2) of encrypted file Date: Tue, 13 Jun 2017 16:47:55 -0700 Message-ID: <20170613234755.111167-4-ebiggers3@gmail.com> References: <20170613234755.111167-1-ebiggers3@gmail.com> 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 To: linux-fscrypt@vger.kernel.org Return-path: In-Reply-To: <20170613234755.111167-1-ebiggers3@gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org 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/ubifs/file.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c index 2cda3d67e2d0..ee3ff4c6bf4a 100644 --- a/fs/ubifs/file.c +++ b/fs/ubifs/file.c @@ -1284,6 +1284,14 @@ int ubifs_setattr(struct dentry *dentry, struct iattr *attr) if (err) return err; + if (ubifs_crypt_is_encrypted(inode) && (attr->ia_valid & ATTR_SIZE)) { + err = fscrypt_get_encryption_info(inode); + if (err) + return err; + if (!fscrypt_has_encryption_key(inode)) + return -ENOKEY; + } + if ((attr->ia_valid & ATTR_SIZE) && attr->ia_size < inode->i_size) /* Truncation to a smaller size */ err = do_truncation(c, inode, attr); -- 2.13.1.508.gb3defc5cc-goog