From 6668ed271eaefaa63e686bdfbedaeb7b8e492722 Mon Sep 17 00:00:00 2001 From: Kumar Kartikeya Dwivedi Date: Fri, 4 Sep 2026 10:43:19 +0200 Subject: selftests/bpf: Reject graph kptr use after RCU unlock Add a sleepable verifier test that loads a graph-node local kptr in an explicit RCU read-side critical section, then passes its node to bpf_rbtree_remove() after the section ends. Before the verifier fix, the stale NON_OWN_REF flag makes the node look like a live borrowed reference and the program is accepted. After the fix, the pointer is demoted without NON_OWN_REF and the graph kfunc argument is rejected. Also exercise a graph kptr loaded while a spin lock provides implicit RCU protection. The pointer must be invalidated when the lock is released, which guards the required ordering between non-owning-reference invalidation and RCU demotion. Update the existing fault-protected load test state description. The post-unlock pointer no longer carries NON_OWN_REF, but remains readable because the load is rewritten to use BPF_PROBE_MEM. Signed-off-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com Signed-off-by: Alexei Starovoitov --- arch/arm64/kvm/pvtime.c | 133 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 133 insertions(+) create mode 100644 arch/arm64/kvm/pvtime.c (limited to 'arch/arm64/kvm/pvtime.c') diff --git a/arch/arm64/kvm/pvtime.c b/arch/arm64/kvm/pvtime.c new file mode 100644 index 000000000..4ceabaa4c --- /dev/null +++ b/arch/arm64/kvm/pvtime.c @@ -0,0 +1,133 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (C) 2019 Arm Ltd. + +#include +#include +#include + +#include +#include + +#include + +void kvm_update_stolen_time(struct kvm_vcpu *vcpu) +{ + struct kvm *kvm = vcpu->kvm; + u64 base = vcpu->arch.steal.base; + u64 last_steal = vcpu->arch.steal.last_steal; + u64 offset = offsetof(struct pvclock_vcpu_stolen_time, stolen_time); + u64 steal = 0; + int idx; + + if (base == INVALID_GPA) + return; + + idx = srcu_read_lock(&kvm->srcu); + if (!kvm_get_guest(kvm, base + offset, steal)) { + steal = le64_to_cpu(steal); + vcpu->arch.steal.last_steal = READ_ONCE(current->sched_info.run_delay); + steal += vcpu->arch.steal.last_steal - last_steal; + kvm_put_guest(kvm, base + offset, cpu_to_le64(steal)); + } + srcu_read_unlock(&kvm->srcu, idx); +} + +long kvm_hypercall_pv_features(struct kvm_vcpu *vcpu) +{ + u32 feature = smccc_get_arg1(vcpu); + long val = SMCCC_RET_NOT_SUPPORTED; + + switch (feature) { + case ARM_SMCCC_HV_PV_TIME_FEATURES: + case ARM_SMCCC_HV_PV_TIME_ST: + if (vcpu->arch.steal.base != INVALID_GPA) + val = SMCCC_RET_SUCCESS; + break; + } + + return val; +} + +gpa_t kvm_init_stolen_time(struct kvm_vcpu *vcpu) +{ + struct pvclock_vcpu_stolen_time init_values = {}; + struct kvm *kvm = vcpu->kvm; + u64 base = vcpu->arch.steal.base; + + if (base == INVALID_GPA) + return base; + + /* + * Start counting stolen time from the time the guest requests + * the feature enabled. + */ + vcpu->arch.steal.last_steal = current->sched_info.run_delay; + kvm_write_guest_lock(kvm, base, &init_values, sizeof(init_values)); + + return base; +} + +bool kvm_arm_pvtime_supported(void) +{ + return !!sched_info_on(); +} + +int kvm_arm_pvtime_set_attr(struct kvm_vcpu *vcpu, + struct kvm_device_attr *attr) +{ + u64 __user *user = (u64 __user *)attr->addr; + struct kvm *kvm = vcpu->kvm; + u64 ipa; + int ret = 0; + int idx; + + if (!kvm_arm_pvtime_supported() || + attr->attr != KVM_ARM_VCPU_PVTIME_IPA) + return -ENXIO; + + if (get_user(ipa, user)) + return -EFAULT; + if (!IS_ALIGNED(ipa, 64)) + return -EINVAL; + if (vcpu->arch.steal.base != INVALID_GPA) + return -EEXIST; + + /* Check the address is in a valid memslot */ + idx = srcu_read_lock(&kvm->srcu); + if (kvm_is_error_hva(gfn_to_hva(kvm, ipa >> PAGE_SHIFT))) + ret = -EINVAL; + srcu_read_unlock(&kvm->srcu, idx); + + if (!ret) + vcpu->arch.steal.base = ipa; + + return ret; +} + +int kvm_arm_pvtime_get_attr(struct kvm_vcpu *vcpu, + struct kvm_device_attr *attr) +{ + u64 __user *user = (u64 __user *)attr->addr; + u64 ipa; + + if (!kvm_arm_pvtime_supported() || + attr->attr != KVM_ARM_VCPU_PVTIME_IPA) + return -ENXIO; + + ipa = vcpu->arch.steal.base; + + if (put_user(ipa, user)) + return -EFAULT; + return 0; +} + +int kvm_arm_pvtime_has_attr(struct kvm_vcpu *vcpu, + struct kvm_device_attr *attr) +{ + switch (attr->attr) { + case KVM_ARM_VCPU_PVTIME_IPA: + if (kvm_arm_pvtime_supported()) + return 0; + } + return -ENXIO; +} -- cgit v1.3.1