From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4C9B83BFE34; Mon, 8 Jun 2026 16:34:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780936483; cv=none; b=aX7R7mKTnSMN69mMpcHefvYdeMwtAqGH7kKNB5JNUtHRdcG+kRcalkFe+pe6J9SPGChpjsdkqAFT6IW/QJU8wAfGRql7G7lqfVS4kdoa9HIZrPRFuR3xjjnjN8M+/GuuhGnffskCD39enfs2FmeZZLPuCFfHKuIGcdh3E87d1hU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780936483; c=relaxed/simple; bh=AXU1tYv3i5R2n9viTtxuEdee5G6RbaLWkstzn8M3FoE=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=rNIzJ14eHlruQyLHwlhKilE1IqIocc16aRQBzQgWOCf9Zby1RFLnyemNbF5RFy6ooAIL3g8odr870kgqsIIMUWvNwpLnivcm5Gpc2nNgcz7wpD5Am4oxhR8cuuAVXo0BnAodUExewfSs9X//rULkPu0euR3G41oxv4pR70qXRiI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KBHtPgxU; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KBHtPgxU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C459F1F00893; Mon, 8 Jun 2026 16:34:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780936481; bh=OQ/DKIjQTR/mHpvMcZ8ruGCqc0pKfen5cUvVayJUDP4=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=KBHtPgxU6DA3m+t/qfjHS3nawDmc+4r6YTzCCMBYT5rtw3yoVBsda6CPjBJ++CpeO aLUYPukZ19n04nmeT5MSKCn4y7LgnjqNZZRgw9f3UVl4InzLI96vqDBR+DD16ybG96 Lx6CEf9M5gQ7YtawbDbJEqJc40EyZpF4UmlJRNjF4Ugw4O7UEbZItrhLqOuQezE4kj iVkcZeYkLTqRzu7i6dGEE3eOW7ljJITenX+2+T8PAbAivmOdXQ0VNGXCh61Z/Xit0N ESQR/jztm0tNg9NqH0dM57M7C+mCSSk5tZdLJXLYsXC33s6lz6eejk5FgiCW7U6lLZ q4WFXw0spz3/w== Date: Mon, 8 Jun 2026 09:34:40 -0700 From: Oliver Upton To: Marc Zyngier Cc: kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Steffen Eiden , Joey Gouly , Suzuki K Poulose , Zenghui Yu Subject: Re: [PATCH] KVM: arm64: Hold kvm->mmu_lock while initialising vcpu->arch.vncr_tlb Message-ID: References: <20260608081108.2244133-1-maz@kernel.org> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260608081108.2244133-1-maz@kernel.org> On Mon, Jun 08, 2026 at 09:11:08AM +0100, Marc Zyngier wrote: > Sashiko reports that there is a race between initialising vncr_tlb > and making use of it, as we don't hold the mmu_lock at this point. > > Additionally, it identifies a memory leak, should userspace repeatedly > invokes the KVM_RUN ioctl after a failure of kvm_arch_vcpu_run_pid_change(), > as we assign vncr_tlb blindly on first run, irrespective of prior > allocations. > > Slap the two bugs in one go by taking the kvm->mmu_lock on assigning > vncr_tlb, preventing the race for good, and by checking that vncr_tlb > is indeed NULL prior to allocation. > > Reported-by: Sashiko > Signed-off-by: Marc Zyngier > Link: https://lore.kernel.org/r/20260607180815.85FBC1F00893@smtp.kernel.org Reviewed-by: Oliver Upton Thanks, Oliver > --- > arch/arm64/kvm/nested.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c > index 690b8e8564166..d11e36b3cfcc2 100644 > --- a/arch/arm64/kvm/nested.c > +++ b/arch/arm64/kvm/nested.c > @@ -1253,8 +1253,14 @@ int kvm_vcpu_allocate_vncr_tlb(struct kvm_vcpu *vcpu) > if (!kvm_has_feat(vcpu->kvm, ID_AA64MMFR4_EL1, NV_frac, NV2_ONLY)) > return 0; > > - vcpu->arch.vncr_tlb = kzalloc_obj(*vcpu->arch.vncr_tlb, > - GFP_KERNEL_ACCOUNT); > + if (!vcpu->arch.vncr_tlb) { > + struct vncr_tlb *vt = kzalloc_obj(*vcpu->arch.vncr_tlb, > + GFP_KERNEL_ACCOUNT); > + > + scoped_guard(write_lock, &vcpu->kvm->mmu_lock) > + vcpu->arch.vncr_tlb = vt; > + } > + > if (!vcpu->arch.vncr_tlb) > return -ENOMEM; > > -- > 2.47.3 >