On Mon, 2023-02-20 at 10:49 +0100, Roberto Sassu wrote:

On Sun, 2023-02-19 at 14:42 -0500, Mimi Zohar wrote:

quoted

On Thu, 2022-12-01 at 11:41 +0100, Roberto Sassu wrote:

quoted

From: Roberto Sassu <roberto.sassu@huawei.com>

Currently, evm_inode_init_security() processes a single LSM xattr from
the array passed by security_inode_init_security(), and calculates the
HMAC on it and other inode metadata.

Given that initxattrs() callbacks, called by
security_inode_init_security(), expect that this array is terminated when
the xattr name is set to NULL, reuse the same assumption to scan all xattrs
and to calculate the HMAC on all of them.

Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
Reviewed-by: Casey Schaufler <casey@schaufler-ca.com>

Normally changing the contents of the EVM HMAC calculation would break
existing systems.  Assuming for the time being this is safe, at what
point will it affect backwards compatability?  Should it be documented
now or then?

Actually, the current patch set continues to fullfill user space
expectation on the EVM behavior. If the LSM infrastructure created more
xattrs and EVM calculated the HMAC on just one, there would be a
problem on subsequent xattr operations and on IMA verification.

By updating both the LSM infrastructure and EVM to support multiple
xattrs, everything will continue to work.

Agreed.  Thank you for the reminder of the bug report being addressed
by this patch set.

Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>

-- 
thanks,

Mimi