On Wed, Aug 18, 2021, Kees Cook wrote:

On Wed, Aug 18, 2021 at 03:11:28PM +0000, Sean Christopherson wrote:

quoted

From dbdca1f4cd01fee418c252e54c360d518b2b1ad6 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <seanjc@google.com>
Date: Wed, 18 Aug 2021 08:03:08 -0700
Subject: [PATCH] KVM: x86: Replace memset() "optimization" with normal
 per-field writes

Explicitly zero select fields in the emulator's decode cache instead of
zeroing the fields via a gross memset() that spans six fields.  gcc and
clang are both clever enough to batch the first five fields into a single
quadword MOV, i.e. memset() and individually zeroing generate identical
code.

Removing the wart also prepares KVM for FORTIFY_SOURCE performing
compile-time and run-time field bounds checking for memset().

No functional change intended.

Reported-by: Kees Cook <redacted>
Signed-off-by: Sean Christopherson <seanjc@google.com>

Reviewed-by: Kees Cook <redacted>

Do you want me to take this patch into my tree, or do you want to carry
it for KVM directly?

That's a Paolo question :-)

What's the expected timeframe for landing stricter bounds checking?  If it's
5.16 or later, the easiest thing would be to squeak this into 5.15.