modpost: Stop grab_file() from leaking filedescriptors if fstat() fails

In case the open() call succeeds but the subsequent fstat() call
fails, then we'll return without close()'ing the filedescriptor.

Signed-off-by: Jesper Juhl <jj@chaosbits.net>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

scripts/mod/modpost.c

@@ -337,17 +337,20 @@ static void sym_update_crc(const char *name, struct module *mod,
 void *grab_file(const char *filename, unsigned long *size)
 {
 	struct stat st;
-	void *map;
+	void *map = MAP_FAILED;
 	int fd;
 
 	fd = open(filename, O_RDONLY);
-	if (fd < 0 || fstat(fd, &st) != 0)
+	if (fd < 0)
 		return NULL;
+	if (fstat(fd, &st))
+		goto failed;
 
 	*size = st.st_size;
 	map = mmap(NULL, *size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
-	close(fd);
 
+failed:
+	close(fd);
 	if (map == MAP_FAILED)
 		return NULL;
 	return map;