From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Marco Elver <elver@google.com>
Cc: stable <stable@vger.kernel.org>, Sasha Levin <sashal@kernel.org>,
Alexander Potapenko <glider@google.com>,
kasan-dev <kasan-dev@googlegroups.com>
Subject: Re: [5.15.y] kfence: default to dynamic branch instead of static keys mode
Date: Wed, 10 Nov 2021 09:31:19 +0100 [thread overview]
Message-ID: <YYuDVxniscyNtBua@kroah.com> (raw)
In-Reply-To: <YYqtuk4r2F9Pal+4@elver.google.com>
On Tue, Nov 09, 2021 at 06:19:54PM +0100, Marco Elver wrote:
> Dear stable maintainers,
>
> We propose picking the following 2 patches to 5.15.y:
>
> 07e8481d3c38 kfence: always use static branches to guard kfence_alloc()
> 4f612ed3f748 kfence: default to dynamic branch instead of static keys mode
>
> , which had not been marked for stable initially, but upon re-evaluation
> conclude that it will also avoid various unexpected behaviours [1], [2]
> as the use of frequently-switched static keys (at least on x86) is more
> trouble than it's worth.
>
> [1] https://lkml.kernel.org/r/CANpmjNOw--ZNyhmn-GjuqU+aH5T98HMmBoCM4z=JFvajC913Qg@mail.gmail.com
> [2] https://patchwork.kernel.org/project/linux-acpi/patch/2618833.mvXUDI8C0e@kreacher/
>
> While optional, we recommend 07e8481d3c38 as well, as it avoids the
> dynamic branch, now the default, if kfence is disabled at boot.
>
> The main thing is to make the default less troublesome and be more
> conservative. Those choosing to enable CONFIG_KFENCE_STATIC_KEYS can
> still do so, but requires a deliberate opt-in via a config change.
Both now queued up, thanks.
greg k-h
prev parent reply other threads:[~2021-11-10 8:31 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-09 17:19 [5.15.y] kfence: default to dynamic branch instead of static keys mode Marco Elver
2021-11-10 8:31 ` Greg Kroah-Hartman [this message]
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