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, 98 insertions, 0 deletions

diff --git a/arch/x86/kvm/Makefile b/arch/x86/kvm/Makefile
new file mode 100644
index 000000000..77337c373
--- /dev/null
+++ b/arch/x86/kvm/Makefile
@@ -0,0 +1,98 @@
+# SPDX-License-Identifier: GPL-2.0
+
+ccflags-y += -I $(srctree)/arch/x86/kvm
+ccflags-$(CONFIG_KVM_WERROR) += -Werror
+
+include $(srctree)/virt/kvm/Makefile.kvm
+
+kvm-y			+= x86.o emulate.o irq.o lapic.o cpuid.o pmu.o mtrr.o \
+			   debugfs.o mmu/mmu.o mmu/page_track.o mmu/spte.o
+
+kvm-$(CONFIG_X86_64) += mmu/tdp_iter.o mmu/tdp_mmu.o
+kvm-$(CONFIG_KVM_IOAPIC) += i8259.o i8254.o ioapic.o
+kvm-$(CONFIG_KVM_HYPERV) += hyperv.o
+kvm-$(CONFIG_KVM_XEN)	+= xen.o
+kvm-$(CONFIG_KVM_SMM)	+= smm.o
+
+kvm-intel-y		+= vmx/vmx.o vmx/vmenter.o vmx/pmu_intel.o vmx/vmcs12.o \
+			   vmx/nested.o vmx/posted_intr.o vmx/main.o
+
+kvm-intel-$(CONFIG_X86_SGX_KVM)	+= vmx/sgx.o
+kvm-intel-$(CONFIG_KVM_HYPERV)	+= vmx/hyperv.o vmx/hyperv_evmcs.o
+kvm-intel-$(CONFIG_KVM_INTEL_TDX)	+= vmx/tdx.o
+
+kvm-amd-y		+= svm/svm.o svm/vmenter.o svm/pmu.o svm/nested.o svm/avic.o
+
+kvm-amd-$(CONFIG_KVM_AMD_SEV)	+= svm/sev.o
+kvm-amd-$(CONFIG_KVM_HYPERV)	+= svm/hyperv.o
+
+ifdef CONFIG_HYPERV
+kvm-y			+= kvm_onhyperv.o
+kvm-intel-y		+= vmx/vmx_onhyperv.o vmx/hyperv_evmcs.o
+kvm-amd-y		+= svm/svm_onhyperv.o
+endif
+
+obj-$(CONFIG_KVM_X86)	+= kvm.o
+obj-$(CONFIG_KVM_INTEL)	+= kvm-intel.o
+obj-$(CONFIG_KVM_AMD)	+= kvm-amd.o
+
+AFLAGS_svm/vmenter.o    := -iquote $(obj)
+$(obj)/svm/vmenter.o: $(obj)/kvm-asm-offsets.h
+
+AFLAGS_vmx/vmenter.o    := -iquote $(obj)
+$(obj)/vmx/vmenter.o: $(obj)/kvm-asm-offsets.h
+
+$(obj)/kvm-asm-offsets.h: $(obj)/kvm-asm-offsets.s FORCE
+	$(call filechk,offsets,__KVM_ASM_OFFSETS_H__)
+
+targets += kvm-asm-offsets.s
+clean-files += kvm-asm-offsets.h
+
+
+# Fail the build if there is unexpected EXPORT_SYMBOL_GPL (or EXPORT_SYMBOL)
+# usage.  All KVM-internal exports should use EXPORT_SYMBOL_FOR_KVM_INTERNAL.
+# Only a handful of exports intended for other modules (VFIO, KVMGT) should
+# use EXPORT_SYMBOL_GPL, and EXPORT_SYMBOL should never be used.
+ifdef CONFIG_KVM_X86
+# Search recursively for whole words and print line numbers.  Filter out the
+# allowed set of exports, i.e. those that are intended for external usage.
+exports_grep_trailer := --include='*.[ch]' -nrw $(srctree)/virt/kvm $(srctree)/arch/x86/kvm | \
+			grep -v -e kvm_page_track_register_notifier \
+				-e kvm_page_track_unregister_notifier \
+				-e kvm_write_track_add_gfn \
+				-e kvm_write_track_remove_gfn \
+				-e kvm_get_kvm \
+				-e kvm_get_kvm_safe \
+				-e kvm_put_kvm
+
+# Force grep to emit a goofy group separator that can in turn be replaced with
+# the above newline macro (newlines in Make are a nightmare).  Note, grep only
+# prints the group separator when N lines of context are requested via -C,
+# a.k.a. --NUM.  Simply request zero lines.  Print the separator only after
+# filtering out expected exports to avoid extra newlines in the error message.
+define get_kvm_exports
+$(shell grep "$(1)" -C0 $(exports_grep_trailer) | grep "$(1)" -C0 --group-separator="!SEP!")
+endef
+
+define check_kvm_exports
+nr_kvm_exports := $(shell grep "$(1)" $(exports_grep_trailer) | wc -l)
+
+ifneq (0,$$(nr_kvm_exports))
+$$(error ERROR ***\
+$$(newline)found $$(nr_kvm_exports) unwanted occurrences of $(1):\
+$$(newline)  $(subst !SEP!,$$(newline) ,$(call get_kvm_exports,$(1)))\
+$$(newline)in directories:\
+$$(newline)  $(srctree)/arch/x86/kvm\
+$$(newline)  $(srctree)/virt/kvm\
+$$(newline)Use EXPORT_SYMBOL_FOR_KVM_INTERNAL, not $(1))
+endif # nr_kvm_exports != 0
+undefine nr_kvm_exports
+endef # check_kvm_exports
+
+$(eval $(call check_kvm_exports,EXPORT_SYMBOL_GPL))
+$(eval $(call check_kvm_exports,EXPORT_SYMBOL))
+
+undefine check_kvm_exports
+undefine get_kvm_exports
+undefine exports_grep_trailer
+endif # CONFIG_KVM_X86