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, 21 insertions, 0 deletions

diff --git a/arch/powerpc/boot/string.h b/arch/powerpc/boot/string.h
new file mode 100644
index 000000000..2b28d1853
--- /dev/null
+++ b/arch/powerpc/boot/string.h
@@ -0,0 +1,21 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _PPC_BOOT_STRING_H_
+#define _PPC_BOOT_STRING_H_
+#include <stddef.h>
+
+extern char *strcpy(char *dest, const char *src);
+extern char *strcat(char *dest, const char *src);
+extern char *strchr(const char *s, int c);
+extern char *strrchr(const char *s, int c);
+extern int strcmp(const char *s1, const char *s2);
+extern int strncmp(const char *s1, const char *s2, size_t n);
+extern size_t strlen(const char *s);
+extern size_t strnlen(const char *s, size_t count);
+
+extern void *memset(void *s, int c, size_t n);
+extern void *memmove(void *dest, const void *src, unsigned long n);
+extern void *memcpy(void *dest, const void *src, unsigned long n);
+extern void *memchr(const void *s, int c, size_t n);
+extern int memcmp(const void *s1, const void *s2, size_t n);
+
+#endif	/* _PPC_BOOT_STRING_H_ */