linux-kernel - Re: [PATCH v2 1/2] KVM: x86: Fix partially uninitialized integer in emulate

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Date: Thu,  8 Feb 2024 16:22:45 -0800
From: Sean Christopherson <seanjc@...gle.com>
To: Sean Christopherson <seanjc@...gle.com>, Paolo Bonzini <pbonzini@...hat.com>, 
	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	"H. Peter Anvin" <hpa@...or.com>, Julian Stecklina <julian.stecklina@...erus-technology.de>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/2] KVM: x86: Fix partially uninitialized integer in emulate_pop

On Mon, 09 Oct 2023 11:20:53 +0200, Julian Stecklina wrote:
> Most code gives a pointer to an uninitialized unsigned long as dest in
> emulate_pop. len is usually the word width of the guest.
> 
> If the guest runs in 16-bit or 32-bit modes, len will not cover the
> whole unsigned long and we end up with uninitialized data in dest.
> 
> Looking through the callers of this function, the issue seems
> harmless, but given that none of this is performance critical, there
> should be no issue with just always initializing the whole value.
> 
> [...]

Applied to kvm-x86 misc.  I massaged the changelog to make it clear that
uninitialized tweaks aren't actually a fix.  I also omitted the change from
a u32=>unsigned long.  The odds of someone copy+pasting em_popa() are lower
than the odds of an unnecessary size change causing some goofy error.

[1/2] KVM: x86: Clean up partially uninitialized integer in emulate_pop()
      https://github.com/kvm-x86/linux/commit/6fd1e3963f20
[2/2] KVM: x86: rename push to emulate_push for consistency
      https://github.com/kvm-x86/linux/commit/64435aaa4a6a

--
https://github.com/kvm-x86/linux/tree/next