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, 29 insertions, 0 deletions

diff --git a/sound/last.c b/sound/last.c
new file mode 100644
index 000000000..f0bb98780
--- /dev/null
+++ b/sound/last.c
@@ -0,0 +1,29 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Advanced Linux Sound Architecture
+ *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
+ */
+
+#include <linux/init.h>
+#include <sound/core.h>
+
+static int __init alsa_sound_last_init(void)
+{
+	struct snd_card *card;
+	int idx, ok = 0;
+	
+	printk(KERN_INFO "ALSA device list:\n");
+	for (idx = 0; idx < SNDRV_CARDS; idx++) {
+		card = snd_card_ref(idx);
+		if (card) {
+			printk(KERN_INFO "  #%i: %s\n", idx, card->longname);
+			snd_card_unref(card);
+			ok++;
+		}
+	}
+	if (ok == 0)
+		printk(KERN_INFO "  No soundcards found.\n");
+	return 0;
+}
+
+late_initcall_sync(alsa_sound_last_init);