Commit 67773a1f authored Jun 13, 2017 by Eric Biggers Committed by Jaegeuk Kim Jul 04, 2017

f2fs: require key for truncate(2) of encrypted file

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 <ebiggers@google.com>
Acked-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

parent 8ceffcb2

fs/f2fs/file.c

+7 −3

Original line number	Diff line number	Diff line
		@@ -710,9 +710,13 @@ 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)) {
		down_write(&F2FS_I(inode)->i_mmap_sem);