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, 50 insertions, 0 deletions

diff --git a/arch/x86/um/Makefile b/arch/x86/um/Makefile
new file mode 100644
index 000000000..f9ea75bf4
--- /dev/null
+++ b/arch/x86/um/Makefile
@@ -0,0 +1,50 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
+#
+
+ifeq ($(CONFIG_X86_32),y)
+	BITS := 32
+else
+	BITS := 64
+endif
+
+obj-y = bugs_$(BITS).o delay.o fault.o \
+	ptrace.o ptrace_$(BITS).o ptrace_user.o setjmp_$(BITS).o signal.o \
+	stub_segv.o \
+	sys_call_table_$(BITS).o sysrq_$(BITS).o tls_$(BITS).o \
+	subarch.o os-Linux/
+
+ifeq ($(CONFIG_X86_32),y)
+
+obj-y += syscalls_32.o
+
+subarch-y = ../lib/string_32.o ../lib/atomic64_32.o ../lib/atomic64_cx8_32.o
+subarch-y += ../lib/cmpxchg8b_emu.o ../lib/atomic64_386_32.o
+subarch-y += ../lib/checksum_32.o
+subarch-y += ../kernel/sys_ia32.o
+
+else
+
+obj-y += mem_64.o syscalls_64.o vdso/
+
+subarch-y = ../lib/csum-partial_64.o ../lib/memcpy_64.o \
+	../lib/memmove_64.o ../lib/memset_64.o
+
+endif
+
+subarch-$(CONFIG_MODULES) += ../kernel/module.o
+
+USER_OBJS := bugs_$(BITS).o ptrace_user.o fault.o
+
+$(obj)/user-offsets.s: c_flags = -Wp,-MD,$(depfile) $(USER_CFLAGS) \
+	-Iarch/x86/include/generated
+targets += user-offsets.s
+
+include/generated/user_constants.h: $(obj)/user-offsets.s FORCE
+	$(call filechk,offsets,__USER_CONSTANT_H__)
+
+UNPROFILE_OBJS := stub_segv.o
+CFLAGS_stub_segv.o := $(CFLAGS_NO_HARDENING)
+
+include $(srctree)/arch/um/scripts/Makefile.rules