linux-kernel - Re: [PATCH 4.19 21/57] proc: dont allow async path resolution of /proc/self components

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Message-ID: <cced67ae-ceca-3812-121c-70e0ed104f49@huawei.com>
Date:   Tue, 2 Mar 2021 16:40:12 +0800
From:   Yang Yingliang <yangyingliang@...wei.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-kernel@...r.kernel.org>
CC:     <stable@...r.kernel.org>, Jens Axboe <axboe@...nel.dk>,
        Sasha Levin <sashal@...nel.org>,
        yangerkun <yangerkun@...wei.com>,
        Cheng Jian <cj.chengjian@...wei.com>
Subject: Re: [PATCH 4.19 21/57] proc: dont allow async path resolution of
 /proc/self components

Hi,

On 2020/12/1 16:53, Greg Kroah-Hartman wrote:
> From: Jens Axboe <axboe@...nel.dk>
>
> [ Upstream commit 8d4c3e76e3be11a64df95ddee52e99092d42fc19 ]
>
> If this is attempted by a kthread, then return -EOPNOTSUPP as we don't
> currently support that. Once we can get task_pid_ptr() doing the right
> thing, then this can go away again.

https://www.spinics.net/lists/io-uring/msg05297.html

This patch seems used for io-wq worker which is merged in

v5.5-rc1, why we need this in linux-4.19.y ?


Thanks,

Yang

>
> Signed-off-by: Jens Axboe <axboe@...nel.dk>
> Signed-off-by: Sasha Levin <sashal@...nel.org>
> ---
>   fs/proc/self.c | 7 +++++++
>   1 file changed, 7 insertions(+)
>
> diff --git a/fs/proc/self.c b/fs/proc/self.c
> index cc6d4253399d1..7922edf70ce1a 100644
> --- a/fs/proc/self.c
> +++ b/fs/proc/self.c
> @@ -16,6 +16,13 @@ static const char *proc_self_get_link(struct dentry *dentry,
>   	pid_t tgid = task_tgid_nr_ns(current, ns);
>   	char *name;
>   
> +	/*
> +	 * Not currently supported. Once we can inherit all of struct pid,
> +	 * we can allow this.
> +	 */
> +	if (current->flags & PF_KTHREAD)
> +		return ERR_PTR(-EOPNOTSUPP);
> +
>   	if (!tgid)
>   		return ERR_PTR(-ENOENT);
>   	/* max length of unsigned int in decimal + NULL term */