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, 61 insertions, 0 deletions

diff --git a/arch/x86/mm/Makefile b/arch/x86/mm/Makefile
new file mode 100644
index 000000000..3a5364853
--- /dev/null
+++ b/arch/x86/mm/Makefile
@@ -0,0 +1,61 @@
+# SPDX-License-Identifier: GPL-2.0
+# Kernel does not boot with instrumentation of tlb.c and mem_encrypt*.c
+KCOV_INSTRUMENT_tlb.o			:= n
+KCOV_INSTRUMENT_mem_encrypt.o		:= n
+KCOV_INSTRUMENT_mem_encrypt_amd.o	:= n
+KCOV_INSTRUMENT_pgprot.o		:= n
+# See the "Disable KCOV" comment in arch/x86/kernel/Makefile.
+KCOV_INSTRUMENT_physaddr.o		:= n
+
+KASAN_SANITIZE_mem_encrypt.o		:= n
+KASAN_SANITIZE_mem_encrypt_amd.o	:= n
+KASAN_SANITIZE_pgprot.o		:= n
+
+# Disable KCSAN entirely, because otherwise we get warnings that some functions
+# reference __initdata sections.
+KCSAN_SANITIZE := n
+# Avoid recursion by not calling KMSAN hooks for CEA code.
+KMSAN_SANITIZE_cpu_entry_area.o := n
+
+ifdef CONFIG_FUNCTION_TRACER
+CFLAGS_REMOVE_mem_encrypt.o		= -pg
+CFLAGS_REMOVE_mem_encrypt_amd.o		= -pg
+CFLAGS_REMOVE_pgprot.o			= -pg
+endif
+
+obj-y				:=  init.o init_$(BITS).o fault.o ioremap.o extable.o mmap.o \
+				    pgtable.o physaddr.o tlb.o cpu_entry_area.o maccess.o pgprot.o
+
+obj-y				+= pat/
+
+# Make sure __phys_addr has no stackprotector
+CFLAGS_physaddr.o		:= -fno-stack-protector
+
+obj-$(CONFIG_X86_32)		+= pgtable_32.o iomap_32.o
+
+obj-$(CONFIG_HUGETLB_PAGE)	+= hugetlbpage.o
+obj-$(CONFIG_PTDUMP)		+= dump_pagetables.o
+obj-$(CONFIG_PTDUMP_DEBUGFS)	+= debug_pagetables.o
+
+KASAN_SANITIZE_kasan_init_$(BITS).o := n
+obj-$(CONFIG_KASAN)		+= kasan_init_$(BITS).o
+
+KMSAN_SANITIZE_kmsan_shadow.o	:= n
+obj-$(CONFIG_KMSAN)		+= kmsan_shadow.o
+
+obj-$(CONFIG_MMIOTRACE)		+= mmiotrace.o
+mmiotrace-y			:= kmmio.o pf_in.o mmio-mod.o
+obj-$(CONFIG_MMIOTRACE_TEST)	+= testmmiotrace.o
+
+obj-$(CONFIG_NUMA)		+= numa.o
+obj-$(CONFIG_AMD_NUMA)		+= amdtopology.o
+obj-$(CONFIG_ACPI_NUMA)		+= srat.o
+
+obj-$(CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS)	+= pkeys.o
+obj-$(CONFIG_RANDOMIZE_MEMORY)			+= kaslr.o
+obj-$(CONFIG_MITIGATION_PAGE_TABLE_ISOLATION)	+= pti.o
+
+obj-$(CONFIG_X86_MEM_ENCRYPT)	+= mem_encrypt.o
+obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt_amd.o
+
+obj-$(CONFIG_AMD_MEM_ENCRYPT)	+= mem_encrypt_boot.o