module: Add hook for security_kernel_post_read_file()

Calls to security_kernel_load_data() should be paired with a call to
security_kernel_post_read_file() with a NULL file argument. Add the
missing call so the module contents are visible to the LSMs interested
in measuring the module content. (This also paves the way for moving
module signature checking out of the module core and into an LSM.)

Cc: Jessica Yu <jeyu@kernel.org>
Fixes: c77b8cdf745d ("module: replace the existing LSM hook in init_module")
Signed-off-by: Kees Cook <keescook@chromium.org>
diff --git a/kernel/module.c b/kernel/module.c
index 0c6573b..af9679f 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -2980,7 +2980,12 @@
 		return -EFAULT;
 	}
 
-	return 0;
+	err = security_kernel_post_read_file(NULL, (char *)info->hdr,
+					     info->len, READING_MODULE);
+	if (err)
+		vfree(info->hdr);
+
+	return err;
 }
 
 static void free_copy(struct load_info *info)