bectl(8): don't allow creation of boot environments with spaces

Boot environment datasets that contain spaces are not bootable.

When a user attempts to create a boot environment with a space, abort
the creation and print an error message.

PR:             254441
Reviewed by:	allanjude
Differential Revision:	https://reviews.freebsd.org/D30194

(cherry picked from commit 0e6549c874)

sbin/bectl/bectl.c

@@ -217,7 +217,10 @@ bectl_cmd_create(int argc, char *argv[])
 	bootenv = *argv;
 
 	err = BE_ERR_SUCCESS;
-	if ((atpos = strchr(bootenv, '@')) != NULL) {
+	if (strchr(bootenv, ' ') != NULL)
+		/* BE datasets with spaces are not bootable */
+		err = BE_ERR_INVALIDNAME;
+	else if ((atpos = strchr(bootenv, '@')) != NULL) {
 		/*
 		 * This is the "create a snapshot variant". No new boot
 		 * environment is to be created here.
@@ -245,6 +248,10 @@ bectl_cmd_create(int argc, char *argv[])
 	switch (err) {
 	case BE_ERR_SUCCESS:
 		break;
+	case BE_ERR_INVALIDNAME:
+		fprintf(stderr,
+		    "bectl create: boot environment name must not contain spaces\n");
+		break;
 	default:
 		if (atpos != NULL)
 			fprintf(stderr,

sbin/bectl/tests/bectl_test.sh

@@ -105,6 +105,10 @@ bectl_create_body()
 	atf_check zfs create -o mountpoint=/usr -o canmount=noauto \
 	    ${zpool}/ROOT/default/usr
 
+	# BE datasets with spaces are not bootable, PR 254441.
+	atf_check -e not-empty -s not-exit:0 \
+		bectl -r ${zpool}/ROOT create "foo bar"
+
 	# Test standard creation, creation of a snapshot, and creation from a
 	# snapshot.
 	atf_check bectl -r ${zpool}/ROOT create -e default default2