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
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