From 6ddb4f372fc63210034b903d96ebbeb3c7195adb Mon Sep 17 00:00:00 2001 From: Oliver Upton Date: Wed, 24 Apr 2024 17:39:58 +0000 Subject: [PATCH 1/2] KVM: arm64: vgic-v2: Check for non-NULL vCPU in vgic_v2_parse_attr() vgic_v2_parse_attr() is responsible for finding the vCPU that matches the user-provided CPUID, which (of course) may not be valid. If the ID is invalid, kvm_get_vcpu_by_id() returns NULL, which isn't handled gracefully. Similar to the GICv3 uaccess flow, check that kvm_get_vcpu_by_id() actually returns something and fail the ioctl if not. Cc: stable@vger.kernel.org Fixes: 7d450e282171 ("KVM: arm/arm64: vgic-new: Add userland access to VGIC dist registers") Reported-by: Alexander Potapenko Tested-by: Alexander Potapenko Reviewed-by: Alexander Potapenko Reviewed-by: Marc Zyngier Link: https://lore.kernel.org/r/20240424173959.3776798-2-oliver.upton@linux.dev Signed-off-by: Oliver Upton --- arch/arm64/kvm/vgic/vgic-kvm-device.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/arm64/kvm/vgic/vgic-kvm-device.c b/arch/arm64/kvm/vgic/vgic-kvm-device.c index f48b8dab8b3d2f..1d26bb5b02f4b5 100644 --- a/arch/arm64/kvm/vgic/vgic-kvm-device.c +++ b/arch/arm64/kvm/vgic/vgic-kvm-device.c @@ -338,12 +338,12 @@ int kvm_register_vgic_device(unsigned long type) int vgic_v2_parse_attr(struct kvm_device *dev, struct kvm_device_attr *attr, struct vgic_reg_attr *reg_attr) { - int cpuid; + int cpuid = FIELD_GET(KVM_DEV_ARM_VGIC_CPUID_MASK, attr->attr); - cpuid = FIELD_GET(KVM_DEV_ARM_VGIC_CPUID_MASK, attr->attr); - - reg_attr->vcpu = kvm_get_vcpu_by_id(dev->kvm, cpuid); reg_attr->addr = attr->attr & KVM_DEV_ARM_VGIC_OFFSET_MASK; + reg_attr->vcpu = kvm_get_vcpu_by_id(dev->kvm, cpuid); + if (!reg_attr->vcpu) + return -EINVAL; return 0; } From 160933e330f4c5a13931d725a4d952a4b9aefa71 Mon Sep 17 00:00:00 2001 From: Oliver Upton Date: Wed, 24 Apr 2024 17:39:59 +0000 Subject: [PATCH 2/2] KVM: selftests: Add test for uaccesses to non-existent vgic-v2 CPUIF Assert that accesses to a non-existent vgic-v2 CPU interface consistently fail across the various KVM device attr ioctls. This also serves as a regression test for a bug wherein KVM hits a NULL dereference when the CPUID specified in the ioctl is invalid. Note that there is no need to print the observed errno, as TEST_ASSERT() will take care of it. Reviewed-by: Marc Zyngier Link: https://lore.kernel.org/r/20240424173959.3776798-3-oliver.upton@linux.dev Signed-off-by: Oliver Upton --- .../testing/selftests/kvm/aarch64/vgic_init.c | 49 +++++++++++++++++++ 1 file changed, 49 insertions(+) diff --git a/tools/testing/selftests/kvm/aarch64/vgic_init.c b/tools/testing/selftests/kvm/aarch64/vgic_init.c index eef816b80993f5..ca917c71ff602d 100644 --- a/tools/testing/selftests/kvm/aarch64/vgic_init.c +++ b/tools/testing/selftests/kvm/aarch64/vgic_init.c @@ -84,6 +84,18 @@ static struct vm_gic vm_gic_create_with_vcpus(uint32_t gic_dev_type, return v; } +static struct vm_gic vm_gic_create_barebones(uint32_t gic_dev_type) +{ + struct vm_gic v; + + v.gic_dev_type = gic_dev_type; + v.vm = vm_create_barebones(); + v.gic_fd = kvm_create_device(v.vm, gic_dev_type); + + return v; +} + + static void vm_gic_destroy(struct vm_gic *v) { close(v->gic_fd); @@ -357,6 +369,40 @@ static void test_vcpus_then_vgic(uint32_t gic_dev_type) vm_gic_destroy(&v); } +#define KVM_VGIC_V2_ATTR(offset, cpu) \ + (FIELD_PREP(KVM_DEV_ARM_VGIC_OFFSET_MASK, offset) | \ + FIELD_PREP(KVM_DEV_ARM_VGIC_CPUID_MASK, cpu)) + +#define GIC_CPU_CTRL 0x00 + +static void test_v2_uaccess_cpuif_no_vcpus(void) +{ + struct vm_gic v; + u64 val = 0; + int ret; + + v = vm_gic_create_barebones(KVM_DEV_TYPE_ARM_VGIC_V2); + subtest_dist_rdist(&v); + + ret = __kvm_has_device_attr(v.gic_fd, KVM_DEV_ARM_VGIC_GRP_CPU_REGS, + KVM_VGIC_V2_ATTR(GIC_CPU_CTRL, 0)); + TEST_ASSERT(ret && errno == EINVAL, + "accessed non-existent CPU interface, want errno: %i", + EINVAL); + ret = __kvm_device_attr_get(v.gic_fd, KVM_DEV_ARM_VGIC_GRP_CPU_REGS, + KVM_VGIC_V2_ATTR(GIC_CPU_CTRL, 0), &val); + TEST_ASSERT(ret && errno == EINVAL, + "accessed non-existent CPU interface, want errno: %i", + EINVAL); + ret = __kvm_device_attr_set(v.gic_fd, KVM_DEV_ARM_VGIC_GRP_CPU_REGS, + KVM_VGIC_V2_ATTR(GIC_CPU_CTRL, 0), &val); + TEST_ASSERT(ret && errno == EINVAL, + "accessed non-existent CPU interface, want errno: %i", + EINVAL); + + vm_gic_destroy(&v); +} + static void test_v3_new_redist_regions(void) { struct kvm_vcpu *vcpus[NR_VCPUS]; @@ -675,6 +721,9 @@ void run_tests(uint32_t gic_dev_type) test_vcpus_then_vgic(gic_dev_type); test_vgic_then_vcpus(gic_dev_type); + if (VGIC_DEV_IS_V2(gic_dev_type)) + test_v2_uaccess_cpuif_no_vcpus(); + if (VGIC_DEV_IS_V3(gic_dev_type)) { test_v3_new_redist_regions(); test_v3_typer_accesses();