apparmor: Fix unpack_profile() warn: passing zero to 'ERR_PTR'

unpack_profile() sets a default error on entry but this gets overridden
by error assignment by functions called in its body. If an error
check that was relying on the default value is triggered after one
of these error assignments then zero will be passed to ERR_PTR.

Fix this by setting up a default -EPROTO assignment in the error
path and while we are at it make sure the correct error is returned
in non-default cases.

Fixes: 217af7e2f4de ("apparmor: refactor profile rules and attachments")
Reported-by: kernel test robot <[e-mail]>
Signed-off-by: John Johansen <[e-mail]>

security/apparmor/policy_unpack.c

···
 		*ns_name = kstrndup(tmpns, ns_len, GFP_KERNEL);
 		if (!*ns_name) {
 			info = "out of memory";
+			error = -ENOMEM;
 			goto fail;
 		}
 		name = tmpname;
···
 		}
 		profile->attach.xmatch_len = tmp;
 		profile->attach.xmatch.start[AA_CLASS_XMATCH] = DFA_START;
-		if (aa_compat_map_xmatch(&profile->attach.xmatch)) {
+		error = aa_compat_map_xmatch(&profile->attach.xmatch);
+		if (error) {
 			info = "failed to convert xmatch permission table";
 			goto fail;
 		}
···
 				      AA_CLASS_FILE);
 		if (!unpack_nameX(e, AA_STRUCTEND, NULL))
 			goto fail;
-		if (aa_compat_map_policy(&rules->policy, e->version)) {
+		error = aa_compat_map_policy(&rules->policy, e->version);
+		if (error) {
 			info = "failed to remap policydb permission table";
 			goto fail;
 		}
···
 	if (error) {
 		goto fail;
 	} else if (rules->file.dfa) {
-		if (aa_compat_map_file(&rules->file)) {
+		error = aa_compat_map_file(&rules->file);
+		if (error) {
 			info = "failed to remap file permission table";
 			goto fail;
 		}
···
 	} else
 		rules->file.dfa = aa_get_dfa(nulldfa);
 
+	error = -EPROTO;
 	if (unpack_nameX(e, AA_STRUCT, "data")) {
 		info = "out of memory";
 		profile->data = kzalloc(sizeof(*profile->data), GFP_KERNEL);
-		if (!profile->data)
+		if (!profile->data) {
+			error = -ENOMEM;
 			goto fail;
-
+		}
 		params.nelem_hint = 3;
 		params.key_len = sizeof(void *);
 		params.key_offset = offsetof(struct aa_data, key);
···
 			data = kzalloc(sizeof(*data), GFP_KERNEL);
 			if (!data) {
 				kfree_sensitive(key);
+				error = -ENOMEM;
 				goto fail;
 			}
 
···
 			if (data->size && !data->data) {
 				kfree_sensitive(data->key);
 				kfree_sensitive(data);
+				error = -ENOMEM;
 				goto fail;
 			}
 
···
 	return profile;
 
 fail:
+	if (error == 0)
+		/* default error covers most cases */
+		error = -EPROTO;
 	if (profile)
 		name = NULL;
 	else if (!name)