Re: [PATCH v5 06/12] evm: Ignore INTEGRITY_NOLABEL/INTEGRITY_NOXATTRS if conditions are safe
From: Mimi Zohar
Date: Tue May 04 2021 - 09:46:16 EST
On Tue, 2021-05-04 at 13:16 +0000, Roberto Sassu wrote:
> > From: Mimi Zohar [mailto:zohar@xxxxxxxxxxxxx]
> > Sent: Monday, May 3, 2021 4:35 PM
> > On Mon, 2021-05-03 at 14:15 +0000, Roberto Sassu wrote:
> >
> > > > > > if (evm_status != INTEGRITY_PASS)
> > > > > > integrity_audit_msg(AUDIT_INTEGRITY_METADATA,
> > > > > d_backing_inode(dentry),
> > > > > > dentry->d_name.name,
> > > > > "appraise_metadata",
> > > > > > @@ -515,7 +535,8 @@ int evm_inode_setattr(struct dentry *dentry,
> > > > struct
> > > > > iattr *attr)
> > > > > > return 0;
> > > > > > evm_status = evm_verify_current_integrity(dentry);
> > > > > > if ((evm_status == INTEGRITY_PASS) ||
> > > > > > - (evm_status == INTEGRITY_NOXATTRS))
> > > > > > + (evm_status == INTEGRITY_NOXATTRS) ||
> > > > > > + (evm_ignore_error_safe(evm_status)))
> > > > >
> > > > > It would also remove the INTEGRITY_NOXATTRS test duplication here.
> > > >
> > > > Ok.
> > >
> > > Actually, it does not seem a duplication. Currently, INTEGRITY_NOXATTRS
> > > is ignored also when the HMAC key is loaded.
> >
> > The existing INTEGRITY_NOXATTRS exemption is more general and includes
> > the new case of when EVM HMAC is disabled. The additional exemption is
> > only needed for INTEGRITY_NOLABEL, when EVM HMAC is disabled.
>
> Unfortunately, evm_ignore_error_safe() is called by both evm_protect_xattr()
> and evm_inode_setattr(). The former requires an exemption also for
> INTEGRITY_NOXATTRS.
>
> I would keep the function as it is. In the worst case, when the status is
> INTEGRITY_NOXATTRS in evm_inode_setattr(), the function will not
> be called.
Right, which is another reason for replacing evm_ignore_eror_safe()
with (is_)evm_hmac_disabled() and inlining the error tests.
thanks,
Mimi