selftests/bpf: Reject graph kptr use after RCU unlockgrafted

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 <memxor@gmail.com>
Link: https://lore.kernel.org/r/20260904084325.52250-7-memxor@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

1 files changed, 133 insertions, 0 deletions

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 <linux/arm-smccc.h>
+#include <linux/kvm_host.h>
+#include <linux/sched/stat.h>
+
+#include <asm/kvm_mmu.h>
+#include <asm/pvclock-abi.h>
+
+#include <kvm/arm_hypercalls.h>
+
+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;
+}