From: Jens Axboe <[email protected]>
To: Pavel Begunkov <[email protected]>, [email protected]
Subject: Re: [RFC][BUG] io_uring: fix work corruption for poll_add
Date: Thu, 23 Jul 2020 16:16:23 -0600 [thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <eaa5b0f65c739072b3f0c9165ff4f9110ae399c4.1595527863.git.asml.silence@gmail.com>
On 7/23/20 12:12 PM, Pavel Begunkov wrote:
> poll_add can have req->work initialised, which will be overwritten in
> __io_arm_poll_handler() because of the union. Luckily, hash_node is
> zeroed in the end, so the damage is limited to lost put for work.creds,
> and probably corrupted work.list.
>
> That's the easiest and really dirty fix, which rearranges members in the
> union, arm_poll*() modifies and zeroes only work.files and work.mm,
> which are never taken for poll add.
> note: io_kiocb is exactly 4 cachelines now.
I don't think there's a way around moving task_work out, just like it
was done on 5.9. The problem is that we could put the environment bits
before doing task_work_add(), but we might need them if the subsequent
queue ends up having to go async. So there's really no know when we can
put them, outside of when the request finishes. Hence, we are kind of
SOL here.
--
Jens Axboe
next prev parent reply other threads:[~2020-07-23 22:16 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-23 18:12 [RFC][BUG] io_uring: fix work corruption for poll_add Pavel Begunkov
2020-07-23 18:15 ` Pavel Begunkov
2020-07-23 18:19 ` Jens Axboe
2020-07-23 19:10 ` Pavel Begunkov
2020-07-23 22:16 ` Jens Axboe [this message]
2020-07-23 22:24 ` Jens Axboe
2020-07-24 12:46 ` Pavel Begunkov
2020-07-24 12:52 ` Pavel Begunkov
2020-07-24 14:12 ` Jens Axboe
2020-07-24 14:23 ` Pavel Begunkov
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
[email protected] \
[email protected] \
[email protected] \
[email protected] \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox