linux-kernel - Re: [PATCH] KVM: arm64: nested: Fix VA sign extension in VNCR/TLBI paths

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Message-ID: <2025090158-kilt-fabulous-3e76@gregkh>
Date: Mon, 1 Sep 2025 22:04:14 +0200
From: Greg KH <gregkh@...uxfoundation.org>
To: Gyujeong Jin <wlsrbwjd7232@...il.com>
Cc: maz@...nel.org, oliver.upton@...ux.dev, joey.gouly@....com,
	suzuki.poulose@....com, yuzenghui@...wei.com,
	catalin.marinas@....com, will@...nel.org, kvmarm@...ts.linux.dev,
	linux-arm-kernel@...ts.infradead.org, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, gyutrange <wlsrbwjd643@...er.com>,
	stable@...r.kernel.org, DongHa Lee <gap-dev@...mple.com>,
	Daehyeon Ko <4ncient@...mple.com>, Geonha Lee <leegn4a@...mple.com>,
	Hyungyu Oh <dqpc_lover@...mple.com>,
	Jaewon Yang <r4mbb1@...mple.com>
Subject: Re: [PATCH] KVM: arm64: nested: Fix VA sign extension in VNCR/TLBI
 paths

On Mon, Sep 01, 2025 at 11:15:51PM +0900, Gyujeong Jin wrote:
> From: gyutrange <wlsrbwjd643@...er.com>
> 
> VNCR/TLBI VA reconstruction currently uses bit 48 as the sign bit,
> but for 48-bit virtual addresses the correct sign bit is bit 47.
> Using 48 can mis-canonicalize addresses in the negative half and may
> cause missed invalidations.
> 
> Although VNCR_EL2 encodes other architectural fields (RESS, BADDR;
> see Arm ARM D24.2.206), sign_extend64() interprets its second argument
> as the index of the sign bit. Passing 48 prevents propagation of the
> canonical sign bit for 48-bit VAs.
> 
> Impact:
> - Incorrect canonicalization of VAs with bit47=1
> - Potential stale VNCR pseudo-TLB entries after TLBI or MMU notifier
> - Possible incorrect translation/permissions or DoS when combined
>   with other issues
> 
> Fixes: 667304740537 ("KVM: arm64: Mask out non-VA bits from TLBI VA* on VNCR invalidation")
> Cc: stable@...r.kernel.org
> Reported-by: DongHa Lee <gap-dev@...mple.com>
> Reported-by: Gyujeong Jin <wlsrbwjd7232@...il.com>
> Reported-by: Daehyeon Ko <4ncient@...mple.com>
> Reported-by: Geonha Lee <leegn4a@...mple.com>
> Reported-by: Hyungyu Oh <dqpc_lover@...mple.com>
> Reported-by: Jaewon Yang <r4mbb1@...mple.com>

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