linux-kernel - Re: [PATCH] coredump: Limit what can interrupt coredumps

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Date:   Sat, 21 Aug 2021 12:47:23 -0400
From:   Olivier Langlois <olivier@...llion01.com>
To:     Jens Axboe <axboe@...nel.dk>,
        Tony Battersby <tonyb@...ernetics.com>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        Oleg Nesterov <oleg@...hat.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        io-uring <io-uring@...r.kernel.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "Pavel Begunkov>" <asml.silence@...il.com>
Subject: Re: [PATCH] coredump: Limit what can interrupt coredumps

On Sat, 2021-08-21 at 06:08 -0400, Olivier Langlois wrote:
> On Tue, 2021-08-17 at 20:57 -0600, Jens Axboe wrote:
> > 
> > Olivier, I sent a 5.10 version for Nathan, any chance you can test
> > this
> > one for the current kernels? Basically this one should work for
> > 5.11+,
> > and the later 5.10 version is just for 5.10. I'm going to send it
> > out
> > separately for review.
> > 
> > I do think this is the right solution, barring a tweak maybe on
> > testing
> > notify == TWA_SIGNAL first before digging into the task struct. But
> > the
> > principle is sound, and it'll work for other users of TWA_SIGNAL as
> > well. None right now as far as I can tell, but the live patching is
> > switching to TIF_NOTIFY_SIGNAL as well which will also cause issues
> > with
> > coredumps potentially.
> > 
> Ok, I am going to give it a shot. This solution is probably superior
> to
> the previous attempt as it does not inject io_uring dependency into
> the
> coredump module.
> 
> The small extra change that I alluded to in my previous reply will
> still be relevant even if we go with your patch...
> 
> I'll come back soon with your patch testing result and my small extra
> change that I keep teasing about.
> 
> Greetings,
> 
Jens,

your patch doesn't compile with 5.12+. AFAIK, the reason is that
JOBCTL_TASK_WORK is gone.

Wouldn't just a call to tracehook_notify_signal from do_coredump be
enough and backward compatible with every possible stable branches?

Greetings,