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, 25 insertions, 0 deletions

diff --git a/arch/mips/sgi-ip30/ip30-console.c b/arch/mips/sgi-ip30/ip30-console.c
new file mode 100644
index 000000000..a5f10097b
--- /dev/null
+++ b/arch/mips/sgi-ip30/ip30-console.c
@@ -0,0 +1,25 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/io.h>
+#include <linux/processor.h>
+
+#include <asm/sn/ioc3.h>
+#include <asm/setup.h>
+
+static inline struct ioc3_uartregs *console_uart(void)
+{
+	struct ioc3 *ioc3;
+
+	ioc3 = (struct ioc3 *)((void *)(0x900000001f600000));
+	return &ioc3->sregs.uarta;
+}
+
+void prom_putchar(char c)
+{
+	struct ioc3_uartregs *uart = console_uart();
+
+	while ((readb(&uart->iu_lsr) & 0x20) == 0)
+		cpu_relax();
+
+	writeb(c, &uart->iu_thr);
+}