From: Kees Cook <keescook@chromium.org>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org, will@kernel.org,
catalin.marinas@arm.com, mark.rutland@arm.com,
Sami Tolvanen <samitolvanen@google.com>
Subject: Re: [PATCH v2 2/2] arm64: Stash shadow stack pointer in the task struct on interrupt
Date: Thu, 12 Jan 2023 14:18:56 -0800 [thread overview]
Message-ID: <202301121418.F0B875E8C@keescook> (raw)
In-Reply-To: <20230109174800.3286265-3-ardb@kernel.org>
On Mon, Jan 09, 2023 at 06:48:00PM +0100, Ard Biesheuvel wrote:
> Instead of reloading the shadow call stack pointer from the ordinary
> stack, which may be vulnerable to the kind of gadget based attacks
> shadow call stacks were designed to prevent, let's store a task's shadow
> call stack pointer in the task struct when switching to the shadow IRQ
> stack.
>
> Given that currently, the task_struct::scs_sp field is only used to
> preserve the shadow call stack pointer while a task is scheduled out or
> running in user space, reusing this field to preserve and restore it
> while running off the IRQ stack must be safe, as those occurrences are
> guaranteed to never overlap. (The stack switching logic only switches
> stacks when running from the task stack, and so the value being saved
> here always corresponds to the task mode shadow stack)
>
> While at it, fold a mov/add/mov sequence into a single add.
>
> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
--
Kees Cook
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next prev parent reply other threads:[~2023-01-12 22:20 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-09 17:47 [PATCH v2 0/2] arm64: harden shadow call stack pointer handling Ard Biesheuvel
2023-01-09 17:47 ` [PATCH v2 1/2] arm64: Always load shadow stack pointer directly from the task struct Ard Biesheuvel
2023-01-10 14:55 ` Mark Rutland
2023-01-12 22:18 ` Kees Cook
2023-01-09 17:48 ` [PATCH v2 2/2] arm64: Stash shadow stack pointer in the task struct on interrupt Ard Biesheuvel
2023-01-10 14:57 ` Mark Rutland
2023-01-12 22:18 ` Kees Cook [this message]
2023-01-20 16:59 ` [PATCH v2 0/2] arm64: harden shadow call stack pointer handling Catalin Marinas
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