criu: Fix open() retval analysing

Negative retval is error, while 0 is OK.

v2: More places

travis-ci: success for criu: Fix open() retval analysing
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>

criu/filesystems.c

@@ -213,7 +213,7 @@ static int write_binfmt_misc_entry(char *mp, char *buf, BinfmtMiscEntry *bme)
 		snprintf(path, PATH_MAX, "%s/%s", mp, bme->name);
 
 		fd = open(path, O_WRONLY);
-		if (!fd) {
+		if (fd < 0) {
 			pr_perror("binfmt_misc: can't open %s", path);
 			goto out;
 		}

criu/sk-packet.c

@@ -325,7 +325,7 @@ static int open_socket_map(int pid, struct vma_area *vm)
 			 */
 
 			fd = dup(le->fe->fd);
-			if (!fd) {
+			if (fd < 0) {
 				pr_perror("Can't dup packet sk");
 				return -1;
 			}

test/zdtm/static/binfmt_misc.c

@@ -120,7 +120,7 @@ int main(int argc, char **argv)
 	/* Register binfmt_entries */
 	sprintf(path, "%s/" "register", dirname);
 	fd = open(path, O_WRONLY);
-	if (!fd) {
+	if (fd < 0) {
 		fail("open");
 		exit(1);
 	}
@@ -145,7 +145,7 @@ int main(int argc, char **argv)
 	/* Disable one of the entries */
 	sprintf(path, "%s/%s", dirname, NAME[0]);
 	fd = open(path, O_WRONLY);
-	if (!fd || write(fd, "0", 1) != 1) {
+	if (fd < 0 || write(fd, "0", 1) != 1) {
 		fail("Can't disable %s\n", path);
 		exit(1);
 	}