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, 55 insertions, 0 deletions

diff --git a/tools/testing/memblock/Makefile b/tools/testing/memblock/Makefile
new file mode 100644
index 000000000..d80982ccd
--- /dev/null
+++ b/tools/testing/memblock/Makefile
@@ -0,0 +1,55 @@
+# SPDX-License-Identifier: GPL-2.0
+
+# Memblock simulator requires AddressSanitizer (libasan) and liburcu development
+# packages installed
+CFLAGS += -I. -I../../include -Wall -O2 -fsanitize=address \
+	  -fsanitize=undefined -D CONFIG_PHYS_ADDR_T_64BIT
+LDFLAGS += -fsanitize=address -fsanitize=undefined
+TARGETS = main
+TEST_OFILES = tests/alloc_nid_api.o tests/alloc_helpers_api.o tests/alloc_api.o \
+		  tests/basic_api.o tests/common.o tests/alloc_exact_nid_api.o
+DEP_OFILES = memblock.o lib/slab.o mmzone.o slab.o cmdline.o
+OFILES = main.o $(DEP_OFILES) $(TEST_OFILES)
+EXTR_SRC = ../../../mm/memblock.c
+
+ifeq ($(BUILD), 32)
+	CFLAGS += -m32
+	LDFLAGS += -m32
+endif
+
+# Process user parameters
+include scripts/Makefile.include
+
+main: $(OFILES)
+
+$(OFILES): include
+
+include: ../../../include/linux/memblock.h ../../include/linux/*.h \
+	../../include/asm/*.h
+
+	@mkdir -p linux
+	test -L linux/memblock.h || ln -s ../../../../include/linux/memblock.h linux/memblock.h
+	test -L asm/asm.h || ln -s ../../../arch/x86/include/asm/asm.h asm/asm.h
+	test -L asm/cmpxchg.h || ln -s ../../../arch/x86/include/asm/cmpxchg.h asm/cmpxchg.h
+
+memblock.c: $(EXTR_SRC)
+	test -L memblock.c || ln -s $(EXTR_SRC) memblock.c
+
+clean:
+	$(RM) $(TARGETS) $(OFILES) linux/memblock.h memblock.c asm/asm.h asm/cmpxchg.h
+
+help:
+	@echo  'Memblock simulator'
+	@echo  ''
+	@echo  'Available targets:'
+	@echo  '  main		  - Build the memblock simulator'
+	@echo  '  clean		  - Remove generated files and symlinks in the directory'
+	@echo  ''
+	@echo  'Configuration:'
+	@echo  '  make MEMBLOCK_DEBUG=1     - enable memblock_dbg() messages'
+	@echo  '  make NUMA=1               - simulate enabled NUMA'
+	@echo  '  make 32BIT_PHYS_ADDR_T=1  - Use 32 bit physical addresses'
+
+vpath %.c ../../lib
+
+.PHONY: clean include help