linux-kernel - Re: FYI: Userland breakage caused by udev bind commit

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Message-ID: <20181224184159.vig2y3mbk2h3kasj@brauner.io>
Date:   Mon, 24 Dec 2018 19:42:00 +0100
From:   Christian Brauner <christian@...uner.io>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Gabriel C <nix.or.die@...il.com>,
        Marcus Meissner <christian.brauner@...onical.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: FYI: Userland breakage caused by udev bind commit

On Mon, Dec 24, 2018 at 10:28:20AM -0800, Linus Torvalds wrote:
> On Mon, Dec 24, 2018 at 10:13 AM Christian Brauner <christian@...uner.io> wrote:
> >
> > So one possibility is to add a socket option for lib/kobject_uevent.c
> > that can be set via setsockopt. We did something like this in netlink
> > for strict property and header checking without breaking backwards
> > compatibility.
> 
> I'd actually prefer for it to be some /sys interface or other. Maybe
> it could even be per-device or class, and you could do something like
> 
>    echo "enable bind" > /sys/bus/serio/uevent
> 
> the uevent code already supports a per-node "filter" function, maybe
> that notion could be extended to also have a filter for uevent types.

Hm, then we maybe we should think about proper kernel-side uevent
filtering at some point (thinking out loud). But that's also a lot of
complexity and I'm not sure that udev users actually would want this.
Would be helpful if a current udev maintainer could comment on this (I
think recently Yu Watanabe stepped up to maintain systemd-udevd? But I
haven't got his mail address.)
But imho, if we can come up with something simple like a flag first as
opt-in we can still allow for more fine-grained filtering later...

Christian

> 
> But I'm just handwaving. Maybe it's better per uevent socket or something.
> 
>               Linus