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, 42 insertions, 0 deletions

diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
new file mode 100644
index 000000000..9295055cd
--- /dev/null
+++ b/arch/arm/lib/Makefile
@@ -0,0 +1,42 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# linux/arch/arm/lib/Makefile
+#
+# Copyright (C) 1995-2000 Russell King
+#
+
+lib-y		:= changebit.o csumipv6.o csumpartial.o               \
+		   csumpartialcopy.o csumpartialcopyuser.o clearbit.o \
+		   delay.o delay-loop.o findbit.o memchr.o memcpy.o   \
+		   memmove.o memset.o setbit.o                        \
+		   strchr.o strrchr.o                                 \
+		   testchangebit.o testclearbit.o testsetbit.o        \
+		   ashldi3.o ashrdi3.o lshrdi3.o muldi3.o             \
+		   ucmpdi2.o lib1funcs.o div64.o                      \
+		   io-readsb.o io-writesb.o io-readsl.o io-writesl.o  \
+		   call_with_stack.o bswapsdi2.o
+
+mmu-y		:= clear_user.o copy_page.o getuser.o putuser.o       \
+		   copy_from_user.o copy_to_user.o
+
+ifdef CONFIG_CC_IS_CLANG
+  lib-y	+= backtrace-clang.o
+else
+  lib-y	+= backtrace.o
+endif
+
+# using lib_ here won't override already available weak symbols
+obj-$(CONFIG_UACCESS_WITH_MEMCPY) += uaccess_with_memcpy.o
+
+lib-$(CONFIG_MMU) += $(mmu-y)
+
+ifeq ($(CONFIG_CPU_32v3),y)
+  lib-y	+= io-readsw-armv3.o io-writesw-armv3.o
+else
+  lib-y	+= io-readsw-armv4.o io-writesw-armv4.o
+endif
+
+$(obj)/csumpartialcopy.o:	$(obj)/csumpartialcopygeneric.S
+$(obj)/csumpartialcopyuser.o:	$(obj)/csumpartialcopygeneric.S
+
+obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o