# Re: \[PATCH v3 06/11\] evm: Ignore INTEGRITY\_NOLABEL if no HMAC key is loaded

- From: Mimi Zohar \<zohar@linux.ibm.com\>
- Date: 2020-12-03 20:43:54 
- List: linux-security-module
- Page: https://ratatoskr.run/linux-security-module/2020/12/194884
- Thread: https://ratatoskr.run/linux-integrity/2020/11/192556/t.md

```text
Hi Roberto,

On Wed, 2020-11-11 at 10:22 +0100, Roberto Sassu wrote:
> When a file is being created, LSMs can set the initial label with the
> inode_init_security hook. If no HMAC key is loaded, the new file will have
> LSM xattrs but not the HMAC.
> 
> Unfortunately, EVM will deny any further metadata operation on new files,
> as evm_protect_xattr() will always return the INTEGRITY_NOLABEL error. This
> would limit the usability of EVM when only a public key is loaded, as
> commands such as cp or tar with the option to preserve xattrs won't work.
> 
> Ignoring this error won't be an issue if no HMAC key is loaded, as the
> inode is locked until the post hook, and EVM won't calculate the HMAC on
> metadata that wasn't previously verified. Thus this patch checks if an
> HMAC key is loaded and if not, ignores INTEGRITY_NOLABEL.

I'm not sure what problem this patch is trying to solve. 
evm_protect_xattr() is only called by evm_inode_setxattr() and
evm_inode_removexattr(), which first checks whether
EVM_ALLOW_METADATA_WRITES is enabled.

Mimi

```