From: Thomas Gleixner <tglx@linutronix.de>
To: Jann Horn <jannh@google.com>
Cc: Andrei Vagin <avagin@gmail.com>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] time/namespace: Forbid timens page faults under kthread_use_mm()
Date: Wed, 30 Nov 2022 01:09:36 +0100 [thread overview]
Message-ID: <87tu2hti9r.ffs@tglx> (raw)
In-Reply-To: <CAG48ez2AqgQJKXYdLXh-WaoMuKBgCUuVge_8RAghKBDhfkeJJw@mail.gmail.com>
On Tue, Nov 29 2022 at 23:34, Jann Horn wrote:
> On Tue, Nov 29, 2022 at 11:28 PM Jann Horn <jannh@google.com> wrote:
>> That said, I haven't actually tried it. But I don't think there's
>> anything in the page fault handling path that distinguishes between
>> copy_from_user() faults in kthread context and other userspace faults
>> in a relevant way?
>
> Ah, but I guess even if this can happen, it's not actually as bad as I
> thought, since kthreads are in init_time_ns, and init_time_ns doesn't
> have a ->vvar_page, so this isn't going to lead to anything terrible
> like page UAF, and it's just a garbage-in-garbage-out scenario.
True, but catching the kthread -> fault (vvar/vdso page) scenario
definitely has a value.
Thanks,
tglx
next prev parent reply other threads:[~2022-11-30 0:09 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-29 19:18 [PATCH 1/2] time/namespace: Refactor copy-pasted helper into one copy Jann Horn
2022-11-29 19:18 ` [PATCH 2/2] time/namespace: Forbid timens page faults under kthread_use_mm() Jann Horn
2022-11-29 21:18 ` Thomas Gleixner
2022-11-29 22:28 ` Jann Horn
2022-11-29 22:34 ` Jann Horn
2022-11-30 0:09 ` Thomas Gleixner [this message]
2022-11-30 0:07 ` Thomas Gleixner
2022-11-30 22:48 ` David Laight
2022-12-01 9:31 ` Jann Horn
2022-11-30 10:15 ` [PATCH 1/2] time/namespace: Refactor copy-pasted helper into one copy Jann Horn
2022-11-30 10:57 ` Thomas Gleixner
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 \
--in-reply-to=87tu2hti9r.ffs@tglx \
--to=tglx@linutronix.de \
--cc=avagin@gmail.com \
--cc=jannh@google.com \
--cc=linux-kernel@vger.kernel.org \
/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