Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Mon, 11 Jun 2018 21:35:24 -0700
From:   Andrey Vagin <avagin@openvz.org>
To:     Konstantin Khorenko <khorenko@virtuozzo.com>
Cc:     Kirill Gorkunov <kgorkunov@virtuozzo.com>,
        Benjamin Coddington <bcodding@redhat.com>,
        Jeff Layton <jlayton@kernel.org>,
        "J. Bruce Fields" <bfields@fieldses.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Vasily Averin <vvs@virtuozzo.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] fs/lock: skip lock owner pid translation in case we
 are in init_pid_ns
Message-ID: <20180612043524.GA8843@outlook.office365.com>
References: <20180608142712.32460-1-khorenko@virtuozzo.com>
 <20180608142712.32460-2-khorenko@virtuozzo.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=koi8-r
Content-Disposition: inline
In-Reply-To: <20180608142712.32460-2-khorenko@virtuozzo.com>
User-Agent: Mutt/1.9.3 (2018-01-21)
Received-SPF: None (protection.outlook.com: virtuozzo.com does not designate
 permitted sender hosts)
SpamDiagnosticOutput: 1:99
SpamDiagnosticMetadata: NSPM
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 12 Jun 2018 04:35:36.4918 (UTC)
X-MS-Exchange-CrossTenant-Network-Message-Id: 3ed62b89-42f2-4a79-3275-08d5d01df279
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 0bc7f26d-0264-416e-a6fc-8352af79c58f
X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM6PR08MB3254
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Fri, Jun 08, 2018 at 05:27:11PM +0300, Konstantin Khorenko wrote:
> If the flock owner process is dead and its pid has been already freed,
> pid translation won't work, but we still want to show flock owner pid
> number when expecting /proc/$PID/fdinfo/$FD in init pidns.
> 
> Reproducer:
> process A	process A1	process A2
> fork()--------->
> exit()		open()
> 		flock()
> 		fork()--------->
> 		exit()		sleep()
> 
> Before the patch:
> ================
> (root@vz7)/: cat /proc/${PID_A2}/fdinfo/3
> pos:    4
> flags:  02100002
> mnt_id: 257
> lock:   (root@vz7)/:
> 
> After the patch:
> ===============
> (root@vz7)/:cat /proc/${PID_A2}/fdinfo/3
> pos:    4
> flags:  02100002
> mnt_id: 295
> lock:   1: FLOCK  ADVISORY  WRITE ${PID_A1} b6:f8a61:529946 0 EOF
> 

Acked-by: Andrey Vagin <avagin@openvz.org>

> Fixes: 9d5b86ac13c5 ("fs/locks: Remove fl_nspid and use fs-specific l_pid for remote locks")
> Signed-off-by: Konstantin Khorenko <khorenko@virtuozzo.com>
> ---
>  fs/locks.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/fs/locks.c b/fs/locks.c
> index 05e211be8684..bfee5b7f2862 100644
> --- a/fs/locks.c
> +++ b/fs/locks.c
> @@ -2072,6 +2072,13 @@ static pid_t locks_translate_pid(struct file_lock *fl, struct pid_namespace *ns)
>  		return -1;
>  	if (IS_REMOTELCK(fl))
>  		return fl->fl_pid;
> +	/*
> +	 * If the flock owner process is dead and its pid has been already
> +	 * freed, the translation below won't work, but we still want to show
> +	 * flock owner pid number in init pidns.
> +	 */
> +	if (ns == &init_pid_ns)
> +		return (pid_t)fl->fl_pid;
>  
>  	rcu_read_lock();
>  	pid = find_pid_ns(fl->fl_pid, &init_pid_ns);
> -- 
> 2.15.1
>