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Date:   Sun, 14 Feb 2021 21:24:33 +0000
From:   Al Viro <viro@zeniv.linux.org.uk>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Jens Axboe <axboe@kernel.dk>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        linux-fsdevel <linux-fsdevel@vger.kernel.org>
Subject: Re: [PATCHSET v3 0/4] fs: Support for LOOKUP_NONBLOCK /
 RESOLVE_NONBLOCK (Insufficiently faking current?)
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On Sun, Feb 14, 2021 at 12:30:07PM -0800, Linus Torvalds wrote:
> On Sun, Feb 14, 2021 at 8:38 AM Jens Axboe <axboe@kernel.dk> wrote:
> >
> > > Similarly it looks like opening of "/dev/tty" fails to
> > > return the tty of the caller but instead fails because
> > > io-wq threads don't have a tty.
> >
> > I've got a patch queued up for 5.12 that clears ->fs and ->files for the
> > thread if not explicitly inherited, and I'm working on similarly
> > proactively catching these cases that could potentially be problematic.
> 
> Well, the /dev/tty case still needs fixing somehow.
> 
> Opening /dev/tty actually depends on current->signal, and if it is
> NULL it will fall back on the first VT console instead (I think).
> 
> I wonder if it should do the same thing /proc/self does..

	I still think that entire "offload pathname resolution to helper
threads" thing is bollocks.  ->fs, ->files and ->signal is still nowhere
near enough - look at /proc/net, for example.  Or netns-sensitive parts
of sysfs, for that matter...  And that's not going into really weird crap
where opener is very special and assumed to be doing all IO.