linux-kernel - Re: [PATCH V2] x86/sev: Mark the code returning to user space as syscall gap

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Message-ID: <CAJhGHyAbSSUnfvDJ1dO2Z56=eRWTj2Ren_mZhGJMHFSPZSjqtg@mail.gmail.com>
Date:   Wed, 27 Apr 2022 16:27:38 +0800
From:   Lai Jiangshan <jiangshanlai@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     X86 ML <x86@...nel.org>,
        Lai Jiangshan <jiangshan.ljs@...group.com>,
        Joerg Roedel <jroedel@...e.de>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Oleg Nesterov <oleg@...hat.com>,
        "Chang S. Bae" <chang.seok.bae@...el.com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH V2] x86/sev: Mark the code returning to user space as
 syscall gap

On Tue, Apr 12, 2022 at 8:48 PM Lai Jiangshan <jiangshanlai@...il.com> wrote:
>
> From: Lai Jiangshan <jiangshan.ljs@...group.com>
>
> When returning to user space, the %rsp is user controlled value.
>
> If it is SNP-guest and the hypervisor decides to mess with the code-page
> for this path while a CPU is executing it.  This will cause a #VC on
> that CPU and that could hit in the syscall return path and mislead
> the #VC handler.
>
> So make ip_within_syscall_gap() return true in this case.
>
> Cc: Joerg Roedel <jroedel@...e.de>
> Signed-off-by: Lai Jiangshan <jiangshan.ljs@...group.com>



Hello

Ping.

Thanks
Lai