Revert "UBUNTU: SAUCE: (namespace) security/integrity: Harden against malformed xattrs"

BugLink: https://bugs.launchpad.net/bugs/1644165

This reverts commit 038b77f6.

The kernel fix for bug #1634964 breaks LXD userspace, in particular the
following commits:

ac7f3f73 (namespace) vfs: Don't modify inodes with a uid or gid unknown to the vfs
ca52383a (namespace) vfs: Don't create inodes with a uid or gid unknown to the vfs

LXD 2.0.6 will include changes to support these kernel changes, but it isn't
available yet on xenial, so for now we just revert these commits.
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

security/integrity/digsig.c

@@ -36,7 +36,7 @@ static const char *keyring_name[INTEGRITY_KEYRING_MAX] = {
 int integrity_digsig_verify(const unsigned int id, const char *sig, int siglen,
 			    const char *digest, int digestlen)
 {
-	if (id >= INTEGRITY_KEYRING_MAX || siglen < 2)
+	if (id >= INTEGRITY_KEYRING_MAX)
 		return -EINVAL;
 
 	if (!keyring[id]) {

security/integrity/evm/evm_main.c

@@ -145,10 +145,6 @@ static enum integrity_status evm_verify_hmac(struct dentry *dentry,
 	/* check value type */
 	switch (xattr_data->type) {
 	case EVM_XATTR_HMAC:
-		if (xattr_len != sizeof(struct evm_ima_xattr_data)) {
-			evm_status = INTEGRITY_FAIL;
-			goto out;
-		}
 		rc = evm_calc_hmac(dentry, xattr_name, xattr_value,
 				   xattr_value_len, calc.digest);
 		if (rc)

security/integrity/ima/ima_appraise.c

@@ -147,8 +147,6 @@ void ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, int xattr_len,
 		break;
 	case IMA_XATTR_DIGEST_NG:
 		hash->algo = xattr_value->digest[0];
-		if (hash->algo >= HASH_ALGO__LAST)
-			hash->algo = ima_hash_algo;
 		break;
 	case IMA_XATTR_DIGEST:
 		/* this is for backward compatibility */