On Mon, 2021-05-03 at 14:48 +0000, Roberto Sassu wrote: > > From: Mimi Zohar [mailto:zohar@xxxxxxxxxxxxx] > > Sent: Monday, May 3, 2021 3:00 PM > > On Wed, 2021-04-07 at 12:52 +0200, Roberto Sassu wrote: > > > > > diff --git a/security/integrity/evm/evm_main.c > > b/security/integrity/evm/evm_main.c > > > @@ -389,6 +473,11 @@ static int evm_protect_xattr(struct > > user_namespace *mnt_userns, > > > if (evm_status == INTEGRITY_FAIL_IMMUTABLE) > > > return 0; > > > > > > + if (evm_status == INTEGRITY_PASS_IMMUTABLE && > > > + !evm_xattr_change(mnt_userns, dentry, xattr_name, xattr_value, > > > + xattr_value_len)) > > > + return 0; > > > + > > > > If the purpose of evm_protect_xattr() is to prevent allowing an invalid > > security.evm xattr from being re-calculated and updated, making it > > valid, INTEGRITY_PASS_IMMUTABLE shouldn't need to be conditional. Any > > time there is an attr or xattr change, including setting it to the > > existing value, the status flag should be reset. > > The status is always reset if evm_protect_xattr() returns 0. This does not > change. > > Not making INTEGRITY_PASS_IMMUTABLE conditional would cause issues. > Suppose that the status is INTEGRITY_FAIL. Writing the same xattr would > cause evm_protect_xattr() to return 0 and the HMAC to be updated. This example is mixing security.evm types. Please clarify. > > I'm wondering if making INTEGRITY_PASS_IMMUTABLE conditional would > > prevent the file from being resigned. > > INTEGRITY_FAIL_IMMUTABLE should be enough to continue the > operation. Agreed. Mimi
