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/include/uapi/asm-generic/poll.h b/include/uapi/asm-generic/poll.h
new file mode 100644
index 000000000..f9c520ce4
--- /dev/null
+++ b/include/uapi/asm-generic/poll.h
@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+#ifndef __ASM_GENERIC_POLL_H
+#define __ASM_GENERIC_POLL_H
+
+/* These are specified by iBCS2 */
+#define POLLIN		0x0001
+#define POLLPRI		0x0002
+#define POLLOUT		0x0004
+#define POLLERR		0x0008
+#define POLLHUP		0x0010
+#define POLLNVAL	0x0020
+
+/* The rest seem to be more-or-less nonstandard. Check them! */
+#define POLLRDNORM	0x0040
+#define POLLRDBAND	0x0080
+#ifndef POLLWRNORM
+#define POLLWRNORM	0x0100
+#endif
+#ifndef POLLWRBAND
+#define POLLWRBAND	0x0200
+#endif
+#ifndef POLLMSG
+#define POLLMSG		0x0400
+#endif
+#ifndef POLLREMOVE
+#define POLLREMOVE	0x1000
+#endif
+#ifndef POLLRDHUP
+#define POLLRDHUP       0x2000
+#endif
+
+#define POLLFREE	(__force __poll_t)0x4000
+
+#define POLL_BUSY_LOOP	(__force __poll_t)0x8000
+
+struct pollfd {
+	int fd;
+	short events;
+	short revents;
+};
+
+#endif	/* __ASM_GENERIC_POLL_H */