Commit 63136858 authored Jun 23, 2017 by Eric Biggers Committed by Theodore Ts'o Jun 23, 2017

ext4: 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>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

parent 66e0aaad

fs/ext4/inode.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -5323,6 +5323,14 @@ 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);

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