From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sasha Levin Subject: [PATCH AUTOSEL 4.14 41/67] KVM: arm/arm64: vgic: Fix possible spectre-v1 write in vgic_mmio_write_apr() Date: Fri, 7 Sep 2018 00:37:52 +0000 Message-ID: <20180907003716.57737-41-alexander.levin@microsoft.com> References: <20180907003716.57737-1-alexander.levin@microsoft.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20180907003716.57737-1-alexander.levin@microsoft.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: "stable@vger.kernel.org" , "linux-kernel@vger.kernel.org" Cc: Mark Rutland , Christoffer Dall , Marc Zyngier , "kvmarm@lists.cs.columbia.edu" , Sasha Levin List-Id: kvmarm@lists.cs.columbia.edu From: Mark Rutland [ Upstream commit 6b8b9a48545e08345b8ff77c9fd51b1aebdbefb3 ] It's possible for userspace to control n. Sanitize n when using it as an array index, to inhibit the potential spectre-v1 write gadget. Note that while it appears that n must be bound to the interval [0,3] due to the way it is extracted from addr, we cannot guarantee that compiler transformations (and/or future refactoring) will ensure this is the case, and given this is a slow path it's better to always perform the masking. Found by smatch. Signed-off-by: Mark Rutland Cc: Christoffer Dall Cc: Marc Zyngier Cc: kvmarm@lists.cs.columbia.edu Signed-off-by: Marc Zyngier Signed-off-by: Sasha Levin --- virt/kvm/arm/vgic/vgic-mmio-v2.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/virt/kvm/arm/vgic/vgic-mmio-v2.c b/virt/kvm/arm/vgic/vgic-mmio= -v2.c index af003268bf3e..7ea5928244fa 100644 --- a/virt/kvm/arm/vgic/vgic-mmio-v2.c +++ b/virt/kvm/arm/vgic/vgic-mmio-v2.c @@ -348,6 +348,9 @@ static void vgic_mmio_write_apr(struct kvm_vcpu *vcpu, =20 if (n > vgic_v3_max_apr_idx(vcpu)) return; + + n =3D array_index_nospec(n, 4); + /* GICv3 only uses ICH_AP1Rn for memory mapped (GICv2) guests */ vgicv3->vgic_ap1r[n] =3D val; } --=20 2.17.1