utils: don't ignore open() return value

In case active console cannot be opened, return NULL early instead
of trying to read from errornous file descriptor.

Coverity CID: 1490087 Argument cannot be negative
Signed-off-by: Daniel Golle <daniel@makrotopia.org>

1 files changed, 6 insertions, 1 deletions

diff --git a/utils/utils.c b/utils/utils.c
index 2cfcc8e..f0c4a90 100644
--- a/utils/utils.c
+++ b/utils/utils.c
@@ -139,7 +139,12 @@ char *get_active_console(char *out, int len)
 {
 	char line[CMDLINE_SIZE + 1];
 	int fd = open("/sys/class/tty/console/active", O_RDONLY);
-	ssize_t r = read(fd, line, sizeof(line) - 1);
+	ssize_t r;
+
+	if (fd < 0)
+		return NULL;
+
+	r = read(fd, line, sizeof(line) - 1);
 	line[CMDLINE_SIZE] = '\0';
 
 	close(fd);