section: Close FD in open_module_self on error

If open_module_map encounters an error, open_module_self would return 0
while leaving the file descriptor open.  Since close_module does not
validate the state of the mod_handle, callers can't know whether to call
close_module when this occurs.

Resolve this by closing the file descriptor before returning so that
mod_handle is never partially open.

Signed-off-by: Kevin Locke <kevin@kevinlocke.name>

src/compat/section-elf.c

@@ -123,7 +123,12 @@ int open_module_self(mod_handle *mod)
         return 0;
 
     mod->fd = fd;
-    return open_module_map(mod);
+    if (!open_module_map(mod)) {
+        close(mod->fd);
+        return 0;
+    }
+
+    return 1;
 }
 
 void close_module(mod_handle *mod)