livepatch/x86_64: Fix the deadlock when insmoding livepatch kernel module

hulk inclusion
category: bugfix
bugzilla: 51843
CVE: NA

---------------------------

In function klp_init_patch, a text_mutex lock is used when
doing jump_label_apply_nops. However, the jump_label_register
in which a text_mutex lock is used is done before the original
text_mutex lock released. Thus, an AA deadlock is occured.

In this commit, we do jump_label_register after the original
text_mutex lock is released to avoid this AA deadlock.
Signed-off-by: NZhao Xuehui <zhaoxuehui1@huawei.com>
Reviewed-by: NKuohai Xu <xukuohai@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

kernel/livepatch/core.c

@@ -1207,14 +1207,12 @@ static int klp_init_patch(struct klp_patch *patch)
 	mutex_lock(&text_mutex);
 	module_disable_ro(patch->mod);
 	jump_label_apply_nops(patch->mod);
+	module_enable_ro(patch->mod, true);
+	mutex_unlock(&text_mutex);
 	ret = jump_label_register(patch->mod);
 	if (ret) {
-		module_enable_ro(patch->mod, true);
-		mutex_unlock(&text_mutex);
 		goto free;
 	}
-	module_enable_ro(patch->mod, true);
-	mutex_unlock(&text_mutex);
 
 #ifdef CONFIG_LIVEPATCH_WO_FTRACE
 	klp_for_each_object(patch, obj)