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[2a02:3100:acb9:201:68d0:34d2:ad1a:175a]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-49b95013d06sm370393515e9.12.2026.08.31.01.10.18 (version=TLS1_3 cipher=TLS_CHACHA20_POLY1305_SHA256 bits=256/256); Mon, 31 Aug 2026 01:10:19 -0700 (PDT) From: Karl Mehltretter To: Marc Zyngier , Oliver Upton , kvmarm@lists.linux.dev Cc: Karl Mehltretter , Fuad Tabba , Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Catalin Marinas , Will Deacon , Paolo Bonzini , Shuah Khan , Eric Auger , Christoffer Dall , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH v4 1/4] KVM: arm64: vgic-v3: Undo assignment on iodev registration failure Date: Mon, 31 Aug 2026 10:10:01 +0200 Message-Id: <20260831081005.41346-2-kmehltretter@gmail.com> X-Mailer: git-send-email 2.39.5 (Apple Git-154) In-Reply-To: <20260831081005.41346-1-kmehltretter@gmail.com> References: <20260831081005.41346-1-kmehltretter@gmail.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit vgic_register_redist_iodev() assigns a redistributor region and base address to the vCPU before adding its iodev to the MMIO bus. However, the region's free_index is advanced only after registration succeeds. If kvm_io_bus_register_dev() fails, the vCPU retains the assignment while free_index still identifies the same slot as free. A later registration can therefore reuse a slot that remains assigned to the vCPU. Reserve the slot before registering its iodev. The caller holds slots_lock, so a registration failure cannot race with a later assignment. Undo the reservation and clear the cached assignment on failure. Fixes: dbd9733ab674 ("KVM: arm/arm64: Replace the single rdist region by a list") Cc: stable@vger.kernel.org Assisted-by: Codex:gpt-5.6-sol Signed-off-by: Karl Mehltretter Reviewed-by: Fuad Tabba --- arch/arm64/kvm/vgic/vgic-mmio-v3.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/arch/arm64/kvm/vgic/vgic-mmio-v3.c b/arch/arm64/kvm/vgic/vgic-mmio-v3.c index 5913a20d8301..22897ce64dbf 100644 --- a/arch/arm64/kvm/vgic/vgic-mmio-v3.c +++ b/arch/arm64/kvm/vgic/vgic-mmio-v3.c @@ -766,6 +766,19 @@ unsigned int vgic_v3_init_dist_iodev(struct vgic_io_device *dev) return SZ_64K; } +static void vgic_undo_redist_assignment(struct kvm_vcpu *vcpu) +{ + struct vgic_cpu *vgic_cpu = &vcpu->arch.vgic_cpu; + + lockdep_assert_held(&vcpu->kvm->slots_lock); + + guard(mutex)(&vcpu->kvm->arch.config_lock); + + vgic_cpu->rdreg->free_index--; + vgic_cpu->rdreg = NULL; + vgic_cpu->rd_iodev.base_addr = VGIC_ADDR_UNDEF; +} + /** * vgic_register_redist_iodev - register a single redist iodev * @vcpu: The VCPU to which the redistributor belongs @@ -818,16 +831,17 @@ int vgic_register_redist_iodev(struct kvm_vcpu *vcpu) rd_dev->nr_regions = ARRAY_SIZE(vgic_v3_rd_registers); rd_dev->redist_vcpu = vcpu; + /* Protected by slots_lock */ + rdreg->free_index++; + mutex_unlock(&kvm->arch.config_lock); ret = kvm_io_bus_register_dev(kvm, KVM_MMIO_BUS, rd_base, 2 * SZ_64K, &rd_dev->dev); if (ret) - return ret; + vgic_undo_redist_assignment(vcpu); - /* Protected by slots_lock */ - rdreg->free_index++; - return 0; + return ret; out_unlock: mutex_unlock(&kvm->arch.config_lock); base-commit: cf72cbb39da84b6f02f90c07f33b102fc10b16f0 -- 2.39.5 (Apple Git-154)