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ubifs: 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: Richard Weinberger <richard@nod.at>
This commit is contained in:
Eric Biggers 2017-06-13 16:47:55 -07:00 committed by Richard Weinberger
parent 32c1431eea
commit 4afb9996a2
1 changed files with 8 additions and 0 deletions
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8
fs/ubifs/file.c
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@ -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);