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, 53 insertions, 0 deletions

diff --git a/tools/lib/cmdline.c b/tools/lib/cmdline.c
new file mode 100644
index 000000000..c85f00f43
--- /dev/null
+++ b/tools/lib/cmdline.c
@@ -0,0 +1,53 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * From lib/cmdline.c
+ */
+#include <stdlib.h>
+
+#if __has_attribute(__fallthrough__)
+# define fallthrough                    __attribute__((__fallthrough__))
+#else
+# define fallthrough                    do {} while (0)  /* fallthrough */
+#endif
+
+unsigned long long memparse(const char *ptr, char **retptr)
+{
+	char *endptr;	/* local pointer to end of parsed string */
+
+	unsigned long long ret = strtoll(ptr, &endptr, 0);
+
+	switch (*endptr) {
+	case 'E':
+	case 'e':
+		ret <<= 10;
+		fallthrough;
+	case 'P':
+	case 'p':
+		ret <<= 10;
+		fallthrough;
+	case 'T':
+	case 't':
+		ret <<= 10;
+		fallthrough;
+	case 'G':
+	case 'g':
+		ret <<= 10;
+		fallthrough;
+	case 'M':
+	case 'm':
+		ret <<= 10;
+		fallthrough;
+	case 'K':
+	case 'k':
+		ret <<= 10;
+		endptr++;
+		fallthrough;
+	default:
+		break;
+	}
+
+	if (retptr)
+		*retptr = endptr;
+
+	return ret;
+}