Merge tag 'audit-pr-20200226' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit

Pull audit fixes from Paul Moore:
"Two fixes for problems found by syzbot:

- Moving audit filter structure fields into a union caused some
problems in the code which populates that filter structure.

We keep the union (that idea is a good one), but we are fixing the
code so that it doesn't needlessly set fields in the union and mess
up the error handling.

- The audit_receive_msg() function wasn't validating user input as
well as it should in all cases, we add the necessary checks"

* tag 'audit-pr-20200226' of git://git.kernel.org/pub/scm/linux/kernel/git/pcmoore/audit:
audit: always check the netlink payload length in audit_receive_msg()
audit: fix error handling in audit_data_to_entry()

kernel/audit.c

···
 	audit_log_end(ab);
 }
 
-static int audit_set_feature(struct sk_buff *skb)
+static int audit_set_feature(struct audit_features *uaf)
 {
-	struct audit_features *uaf;
 	int i;
 
 	BUILD_BUG_ON(AUDIT_LAST_FEATURE + 1 > ARRAY_SIZE(audit_feature_names));
-	uaf = nlmsg_data(nlmsg_hdr(skb));
 
 	/* if there is ever a version 2 we should handle that here */
 
···
 {
 	u32			seq;
 	void			*data;
+	int			data_len;
 	int			err;
 	struct audit_buffer	*ab;
 	u16			msg_type = nlh->nlmsg_type;
···
 
 	seq  = nlh->nlmsg_seq;
 	data = nlmsg_data(nlh);
+	data_len = nlmsg_len(nlh);
 
 	switch (msg_type) {
 	case AUDIT_GET: {
···
 		struct audit_status	s;
 		memset(&s, 0, sizeof(s));
 		/* guard against past and future API changes */
-		memcpy(&s, data, min_t(size_t, sizeof(s), nlmsg_len(nlh)));
+		memcpy(&s, data, min_t(size_t, sizeof(s), data_len));
 		if (s.mask & AUDIT_STATUS_ENABLED) {
 			err = audit_set_enabled(s.enabled);
 			if (err < 0)
···
 			return err;
 		break;
 	case AUDIT_SET_FEATURE:
-		err = audit_set_feature(skb);
+		if (data_len < sizeof(struct audit_features))
+			return -EINVAL;
+		err = audit_set_feature(data);
 		if (err)
 			return err;
 		break;
···
 
 		err = audit_filter(msg_type, AUDIT_FILTER_USER);
 		if (err == 1) { /* match or error */
+			char *str = data;
+
 			err = 0;
 			if (msg_type == AUDIT_USER_TTY) {
 				err = tty_audit_push();
···
 					break;
 			}
 			audit_log_user_recv_msg(&ab, msg_type);
-			if (msg_type != AUDIT_USER_TTY)
+			if (msg_type != AUDIT_USER_TTY) {
+				/* ensure NULL termination */
+				str[data_len - 1] = '\0';
 				audit_log_format(ab, " msg='%.*s'",
 						 AUDIT_MESSAGE_TEXT_MAX,
-						 (char *)data);
-			else {
-				int size;
-
+						 str);
+			} else {
 				audit_log_format(ab, " data=");
-				size = nlmsg_len(nlh);
-				if (size > 0 &&
-				    ((unsigned char *)data)[size - 1] == '\0')
-					size--;
-				audit_log_n_untrustedstring(ab, data, size);
+				if (data_len > 0 && str[data_len - 1] == '\0')
+					data_len--;
+				audit_log_n_untrustedstring(ab, str, data_len);
 			}
 			audit_log_end(ab);
 		}
 		break;
 	case AUDIT_ADD_RULE:
 	case AUDIT_DEL_RULE:
-		if (nlmsg_len(nlh) < sizeof(struct audit_rule_data))
+		if (data_len < sizeof(struct audit_rule_data))
 			return -EINVAL;
 		if (audit_enabled == AUDIT_LOCKED) {
 			audit_log_common_recv_msg(audit_context(), &ab,
···
 			audit_log_end(ab);
 			return -EPERM;
 		}
-		err = audit_rule_change(msg_type, seq, data, nlmsg_len(nlh));
+		err = audit_rule_change(msg_type, seq, data, data_len);
 		break;
 	case AUDIT_LIST_RULES:
 		err = audit_list_rules_send(skb, seq);
···
 	case AUDIT_MAKE_EQUIV: {
 		void *bufp = data;
 		u32 sizes[2];
-		size_t msglen = nlmsg_len(nlh);
+		size_t msglen = data_len;
 		char *old, *new;
 
 		err = -EINVAL;
···
 
 		memset(&s, 0, sizeof(s));
 		/* guard against past and future API changes */
-		memcpy(&s, data, min_t(size_t, sizeof(s), nlmsg_len(nlh)));
+		memcpy(&s, data, min_t(size_t, sizeof(s), data_len));
 		/* check if new data is valid */
 		if ((s.enabled != 0 && s.enabled != 1) ||
 		    (s.log_passwd != 0 && s.log_passwd != 1))

kernel/auditfilter.c

···
 	bufp = data->buf;
 	for (i = 0; i < data->field_count; i++) {
 		struct audit_field *f = &entry->rule.fields[i];
+		u32 f_val;
 
 		err = -EINVAL;
 
···
 			goto exit_free;
 
 		f->type = data->fields[i];
-		f->val = data->values[i];
+		f_val = data->values[i];
 
 		/* Support legacy tests for a valid loginuid */
-		if ((f->type == AUDIT_LOGINUID) && (f->val == AUDIT_UID_UNSET)) {
+		if ((f->type == AUDIT_LOGINUID) && (f_val == AUDIT_UID_UNSET)) {
 			f->type = AUDIT_LOGINUID_SET;
-			f->val = 0;
+			f_val = 0;
 			entry->rule.pflags |= AUDIT_LOGINUID_LEGACY;
 		}
 
···
 		case AUDIT_SUID:
 		case AUDIT_FSUID:
 		case AUDIT_OBJ_UID:
-			f->uid = make_kuid(current_user_ns(), f->val);
+			f->uid = make_kuid(current_user_ns(), f_val);
 			if (!uid_valid(f->uid))
 				goto exit_free;
 			break;
···
 		case AUDIT_SGID:
 		case AUDIT_FSGID:
 		case AUDIT_OBJ_GID:
-			f->gid = make_kgid(current_user_ns(), f->val);
+			f->gid = make_kgid(current_user_ns(), f_val);
 			if (!gid_valid(f->gid))
 				goto exit_free;
 			break;
 		case AUDIT_ARCH:
+			f->val = f_val;
 			entry->rule.arch_f = f;
 			break;
 		case AUDIT_SUBJ_USER:
···
 		case AUDIT_OBJ_TYPE:
 		case AUDIT_OBJ_LEV_LOW:
 		case AUDIT_OBJ_LEV_HIGH:
-			str = audit_unpack_string(&bufp, &remain, f->val);
-			if (IS_ERR(str))
+			str = audit_unpack_string(&bufp, &remain, f_val);
+			if (IS_ERR(str)) {
+				err = PTR_ERR(str);
 				goto exit_free;
-			entry->rule.buflen += f->val;
-
+			}
+			entry->rule.buflen += f_val;
+			f->lsm_str = str;
 			err = security_audit_rule_init(f->type, f->op, str,
 						       (void **)&f->lsm_rule);
 			/* Keep currently invalid fields around in case they
···
 				pr_warn("audit rule for LSM \'%s\' is invalid\n",
 					str);
 				err = 0;
-			}
-			if (err) {
-				kfree(str);
+			} else if (err)
 				goto exit_free;
-			} else
-				f->lsm_str = str;
 			break;
 		case AUDIT_WATCH:
-			str = audit_unpack_string(&bufp, &remain, f->val);
-			if (IS_ERR(str))
+			str = audit_unpack_string(&bufp, &remain, f_val);
+			if (IS_ERR(str)) {
+				err = PTR_ERR(str);
 				goto exit_free;
-			entry->rule.buflen += f->val;
-
-			err = audit_to_watch(&entry->rule, str, f->val, f->op);
+			}
+			err = audit_to_watch(&entry->rule, str, f_val, f->op);
 			if (err) {
 				kfree(str);
 				goto exit_free;
 			}
+			entry->rule.buflen += f_val;
 			break;
 		case AUDIT_DIR:
-			str = audit_unpack_string(&bufp, &remain, f->val);
-			if (IS_ERR(str))
+			str = audit_unpack_string(&bufp, &remain, f_val);
+			if (IS_ERR(str)) {
+				err = PTR_ERR(str);
 				goto exit_free;
-			entry->rule.buflen += f->val;
-
+			}
 			err = audit_make_tree(&entry->rule, str, f->op);
 			kfree(str);
 			if (err)
 				goto exit_free;
+			entry->rule.buflen += f_val;
 			break;
 		case AUDIT_INODE:
+			f->val = f_val;
 			err = audit_to_inode(&entry->rule, f);
 			if (err)
 				goto exit_free;
 			break;
 		case AUDIT_FILTERKEY:
-			if (entry->rule.filterkey || f->val > AUDIT_MAX_KEY_LEN)
+			if (entry->rule.filterkey || f_val > AUDIT_MAX_KEY_LEN)
 				goto exit_free;
-			str = audit_unpack_string(&bufp, &remain, f->val);
-			if (IS_ERR(str))
-				goto exit_free;
-			entry->rule.buflen += f->val;
-			entry->rule.filterkey = str;
-			break;
-		case AUDIT_EXE:
-			if (entry->rule.exe || f->val > PATH_MAX)
-				goto exit_free;
-			str = audit_unpack_string(&bufp, &remain, f->val);
+			str = audit_unpack_string(&bufp, &remain, f_val);
 			if (IS_ERR(str)) {
 				err = PTR_ERR(str);
 				goto exit_free;
 			}
-			entry->rule.buflen += f->val;
-
-			audit_mark = audit_alloc_mark(&entry->rule, str, f->val);
+			entry->rule.buflen += f_val;
+			entry->rule.filterkey = str;
+			break;
+		case AUDIT_EXE:
+			if (entry->rule.exe || f_val > PATH_MAX)
+				goto exit_free;
+			str = audit_unpack_string(&bufp, &remain, f_val);
+			if (IS_ERR(str)) {
+				err = PTR_ERR(str);
+				goto exit_free;
+			}
+			audit_mark = audit_alloc_mark(&entry->rule, str, f_val);
 			if (IS_ERR(audit_mark)) {
 				kfree(str);
 				err = PTR_ERR(audit_mark);
 				goto exit_free;
 			}
+			entry->rule.buflen += f_val;
 			entry->rule.exe = audit_mark;
+			break;
+		default:
+			f->val = f_val;
 			break;
 		}
 	}