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

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Date:   Sat, 21 Aug 2021 10:51:13 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Olivier Langlois <olivier@...llion01.com>,
        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 8/21/21 10:47 AM, Olivier Langlois wrote:
> 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?

That version is just for 5.10, the first I posted is applicable to
5.11+

-- 
Jens Axboe