From: Joerg Roedel <jroedel@suse.de>
To: Arvind Sankar <nivedita@alum.mit.edu>
Cc: Joerg Roedel <joro@8bytes.org>,
x86@kernel.org, Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Andy Lutomirski <luto@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Kees Cook <keescook@chromium.org>,
Martin Radev <martin.b.radev@gmail.com>,
Tom Lendacky <thomas.lendacky@amd.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/5] x86/boot/compressed/64: Check SEV encryption in 64-bit boot-path
Date: Tue, 20 Oct 2020 10:59:57 +0200 [thread overview]
Message-ID: <20201020085957.GF9328@suse.de> (raw)
In-Reply-To: <20201019213106.GB2815942@rani.riverdale.lan>
On Mon, Oct 19, 2020 at 05:31:06PM -0400, Arvind Sankar wrote:
> Is it possible to take advantage of this to make the check independent
> of the original page tables? i.e. switch to the new pagetables, then
> write into .data or .bss the opcodes for a function that does
> movabs $imm64, %rax
> jmp *%rdi // avoid using stack for the return
> filling in the imm64 with the RDRAND value, and then try to execute it.
> If the C-bit value is wrong, this will probably crash, and at any rate
> shouldn't return with the correct value in %rax.
That could work, but is not reliable. When the C bit is wrong the CPU
would essentially execute random data, which could also be a valid
instruction stream. A crash is not guaranteed.
Regards,
Joerg
next prev parent reply other threads:[~2020-10-20 9:00 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-19 15:11 [PATCH 0/5] x86/sev-es: Mitigate some HV attack vectors Joerg Roedel
2020-10-19 15:11 ` [PATCH 1/5] x86/boot/compressed/64: Introduce sev_status Joerg Roedel
2020-10-20 0:59 ` Sean Christopherson
2020-10-20 1:08 ` Sean Christopherson
2020-10-20 9:55 ` Joerg Roedel
2020-10-19 15:11 ` [PATCH 2/5] x86/boot/compressed/64: Add CPUID sanity check to early #VC handler Joerg Roedel
2020-10-19 15:11 ` [PATCH 3/5] x86/boot/compressed/64: Check SEV encryption in 64-bit boot-path Joerg Roedel
2020-10-19 17:00 ` Arvind Sankar
2020-10-19 17:54 ` Arvind Sankar
2020-10-19 20:39 ` Joerg Roedel
2020-10-19 21:31 ` Arvind Sankar
2020-10-20 8:59 ` Joerg Roedel [this message]
2020-10-20 14:33 ` Arvind Sankar
2020-10-20 15:44 ` Joerg Roedel
2020-10-19 20:33 ` Joerg Roedel
2020-10-19 21:22 ` Arvind Sankar
2020-10-20 9:41 ` Joerg Roedel
2020-10-19 15:11 ` [PATCH 4/5] x86/head/64: Check SEV encryption before switching to kernel page-table Joerg Roedel
2020-10-19 15:11 ` [PATCH 5/5] x86/sev-es: Do not support MMIO to/from encrypted memory Joerg Roedel
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