linux-kernel - RE: Is it possible to add pid and comm members to the event structure to increase the display of user and thread information?

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Message-ID: <E490CD805F7529488761C40FD9D26EF12A7A5ADA@dggemm507-mbs.china.huawei.com>
Date:   Thu, 13 Sep 2018 11:25:28 +0000
From:   Nixiaoming <nixiaoming@...wei.com>
To:     Amir Goldstein <amir73il@...il.com>
CC:     Eric Paris <eparis@...isplace.org>, Robert Love <rlove@...ve.org>,
        "John McCutchan" <john@...nmccutchan.com>, Jan Kara <jack@...e.cz>,
        Al Viro <viro@...iv.linux.org.uk>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: RE: Is it possible to add pid and comm members to the event
 structure to increase the display of user and thread information?

On Tue, Sep 11, 2018 at 11:12 PM Amir Goldstein <amir73il@...il.com> wrote:
>On Tue, Sep 11, 2018 at 9:51 AM Nixiaoming <nixiaoming@...wei.com> wrote:
>>
>> Inotify api cannot display information about users and processes.
>> That is, you can only know that the file event is generated, but you don't know who triggered the event, which is not conducive to fault location.
>> Is it possible to add pid and comm members to the event structure to increase the display of user and thread information?
>>
>
>"Is it possible?" is not the only relevant question.
>I suppose your patch can sort of works, but it exposes information to
>potentially unpriveleged
>processes, even exposes pid values outside of the process pid namespace.
>
>While those issues could be addressed, you can't change the format
>struct inotify_event
>without breaking existing applications.
>
In order to improve the fault location capability, can we make incompatible interface changes?

>I guess you are not using fanotify API, which already provides pid
>information (albiet tgid),
>because it lacks other functionality that you need? Which
>functionality might that be?
>Is it directory modification events?
>If so than you might be interested in my effort to add support for
>those events to fanotify:
>https://github.com/amir73il/fsnotify-utils/wiki/Super-block-root-watch
>
The fanotify API does not support monitoring file deletion events
The fanotify API supports tgid display,
but for multi-threaded programs,
it still cannot accurately identify which thread triggered the event.
Can I modify tgid to pid?
- event->tgid = get_pid(task_tgid(current));
+ event->tgid = get_pid(task_pid(current));

>Your support, should you choose to offer it, could be in the form of
>testing patches
>and/or just by putting forward your use case as an example for the
>need of an extended
>fanotify API.
>
>Thanks,
>Amir.
>

Thanks