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

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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);