On Mon Aug 5, 2024 at 2:54 PM EEST, Jann Horn wrote:

keyctl_session_to_parent() involves posting task work to the parent task,
with work function key_change_session_keyring.
Because the task work in the parent runs asynchronously, no errors can be
returned back to the caller of keyctl_session_to_parent(), and therefore
the work function key_change_session_keyring() can't be allowed to fail due
to things like memory allocation failure or permission checks - all
allocations and checks have to happen in the child.

This is annoying for two reasons:

 - It is the only reason why cred_alloc_blank() and
   security_transfer_creds() are necessary.
 - It means we can't do synchronous permission checks.

I agree with this premise. Also I think the code change is reasonable.

I'd like to see a comment from David tho.

BR, Jarkko