[Toybox] [PATCH] losetup: Wait for ueventd to create loop device on Android

[enh]

On Sat, Aug 27, 2022 at 5:01 AM Rob Landley <rob at landley.net> wrote:

> On 8/25/22 09:52, enh wrote:
> > On Thu, Aug 25, 2022 at 1:05 AM Rob Landley <rob at landley.net> wrote:
> >
> >     What would have made SENSE was having the netlink hotplug interface
> (ala
> >     nlmsg_type = RTM_GETLINK) register to say it's going to send back
> response
> >     packets with credential info for each new node (something vaguely
> like
> >     nlmsghdr.nlmsg_flags = BLAH|NLM_F_SETCRED;) then having device node
> creation
> >     wait for the userspace credential request the same way it waits for
> a userspace
> >     firmware load request. You could even watchdog it where a timeout
> causes the
> >     device creation to return error and not make the node, and if the
> netlink
> >     program exits without properly deregistering (and a new instance
> doesn't
> >     restart) then that's gonna time out, meaning you can't do a security
> attack by
> >     trying to kill the daemon. (DOS sure, but show me a daemon kill that
> doesn't
> >     deny service.) And if you fire up the netlink daemon before mounting
> devtmpfs
> >     for the first time, it gets to annotate all the initial device node
> creations in
> >     a cleanish way so they're never exposed without credentials.
> >
> > yeah, from what i remember, that's roughly what the people who actually
> know
> > what they're talking about said that they'd need. but that's also what
> they
> > thought they wouldn't be able to get upstream in any
> realistically-spendable
> > amount of time.
>
> I don't suppose anyone ever roughed up a kernel patch?
>

not that i remember or could find any evidence of. given that we'd need a
userspace component anyway, and already have a working one, it was unclear
that it would bring anything but disruption, new bugs, and a bunch of time
spent arguing with upstream over something we didn't really _need_ anyway.

see also
https://www.mail-archive.com/seandroid-list@tycho.nsa.gov/msg02393.html
(and the rest of the thread) for thoughts from someone who probably looked
into it the most. (and that thread also ends with "what's the practical
benefit [of moving to devtmpfs]?" with no answer.)


> Rob
>
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