linux-kernel - [PATCH 0/3] x86/sev-es: Check for trusted regs->sp in __sev_es_ist

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Message-Id: <20210217120143.6106-1-joro@8bytes.org>
Date:   Wed, 17 Feb 2021 13:01:40 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     x86@...nel.org
Cc:     Joerg Roedel <joro@...tes.org>, Joerg Roedel <jroedel@...e.de>,
        hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Martin Radev <martin.b.radev@...il.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        virtualization@...ts.linux-foundation.org
Subject: [PATCH 0/3] x86/sev-es: Check for trusted regs->sp in __sev_es_ist_enter()

From: Joerg Roedel <jroedel@...e.de>

Hi,

here are some changes to the Linux SEV-ES code to check whether the
value in regs->sp can be trusted, before checking whether it points to
the #VC IST stack.

Andy Lutomirski reported that it is entirely possible to reach this
function with a regs->sp value which was set by user-space. So check
for this condition and don't use regs->sp if it can't be trusted.

Also improve the comments around __sev_es_ist_enter/exit() to better
explain what these function do and why they are there.

Please review.

Thanks,

	Joerg

Joerg Roedel (3):
  x86/sev-es: Introduce from_syscall_gap() helper
  x86/sev-es: Check if regs->sp is trusted before adjusting #VC IST
    stack
  x86/sev-es: Improve comments in and around __sev_es_ist_enter/exit()

 arch/x86/include/asm/ptrace.h |  8 ++++++++
 arch/x86/kernel/sev-es.c      | 27 +++++++++++++++++++--------
 arch/x86/kernel/traps.c       |  3 +--
 3 files changed, 28 insertions(+), 10 deletions(-)

-- 
2.30.0