libkmod: Treat illegal modinfo file as error

The file modules.builtin.modinfo is supposed to consist of NUL
terminated strings. If the file contains a string which is not
properly NUL terminated, treat it as error.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>

libkmod/libkmod-builtin.c

@@ -141,6 +141,10 @@ static off_t get_string(struct kmod_builtin_iter *iter, off_t offset,
 	}
 
 	if (linesz) {
+		if (iter->buf[linesz - 1] != '\0') {
+			sv_errno = EINVAL;
+			goto fail;
+		}
 		*line = iter->buf;
 		*size = linesz;
 	}