Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 25 Jul 2023 10:26:19 +0200
From:   Christian Brauner <brauner@kernel.org>
To:     Xuewen Yan <xuewen.yan@unisoc.com>
Cc:     jack@suse.cz, keescook@chromium.org, peterz@infradead.org,
        vincent.guittot@linaro.org, linux-kernel@vger.kernel.org,
        di.shen@unisoc.com
Subject: Re: [PATCH] pid: Add the judgment of whether ns is NULL in the
 find_pid_ns
Message-ID: <20230725-hemmschwelle-braten-481527898001@brauner>
References: <20230713071713.5762-1-xuewen.yan@unisoc.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Disposition: inline
In-Reply-To: <20230713071713.5762-1-xuewen.yan@unisoc.com>
Precedence: bulk

On Thu, Jul 13, 2023 at 03:17:13PM +0800, Xuewen Yan wrote:
> There is no the judgment of whether namspace is NULL in find_pid_ns.
> But there is a corner case when ns is null, for example: if user
> call find_get_pid when current is in exiting, the following stack would
> set thread_id be null:
> release_task
>     __exit_signal(p);
>         __unhash_process(tsk, group_dead);
>               detach_pid(p, PIDTYPE_PID);
>                   __change_pid(task, type, NULL);
> 
> If user call find_get_pid at now, in find_vpid function, the

I fail to see how this can happen. The code you're referencing is in
release_task(). If current has gone through that then current obviously
can't call find_vpid() on itself anymore or anything else for that
matter.