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, 122 insertions, 0 deletions

diff --git a/sound/firewire/fireface/ff-midi.c b/sound/firewire/fireface/ff-midi.c
new file mode 100644
index 000000000..9f6aa490e
--- /dev/null
+++ b/sound/firewire/fireface/ff-midi.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * ff-midi.c - a part of driver for RME Fireface series
+ *
+ * Copyright (c) 2015-2017 Takashi Sakamoto
+ */
+
+#include "ff.h"
+
+static int midi_capture_open(struct snd_rawmidi_substream *substream)
+{
+	/* Do nothing. */
+	return 0;
+}
+
+static int midi_playback_open(struct snd_rawmidi_substream *substream)
+{
+	struct snd_ff *ff = substream->rmidi->private_data;
+
+	/* Initialize internal status. */
+	ff->on_sysex[substream->number] = 0;
+	ff->rx_midi_error[substream->number] = false;
+
+	WRITE_ONCE(ff->rx_midi_substreams[substream->number], substream);
+
+	return 0;
+}
+
+static int midi_capture_close(struct snd_rawmidi_substream *substream)
+{
+	/* Do nothing. */
+	return 0;
+}
+
+static int midi_playback_close(struct snd_rawmidi_substream *substream)
+{
+	struct snd_ff *ff = substream->rmidi->private_data;
+
+	cancel_work_sync(&ff->rx_midi_work[substream->number]);
+	WRITE_ONCE(ff->rx_midi_substreams[substream->number], NULL);
+
+	return 0;
+}
+
+static void midi_capture_trigger(struct snd_rawmidi_substream *substream,
+				 int up)
+{
+	struct snd_ff *ff = substream->rmidi->private_data;
+
+	guard(spinlock_irqsave)(&ff->lock);
+
+	if (up)
+		WRITE_ONCE(ff->tx_midi_substreams[substream->number],
+			   substream);
+	else
+		WRITE_ONCE(ff->tx_midi_substreams[substream->number], NULL);
+}
+
+static void midi_playback_trigger(struct snd_rawmidi_substream *substream,
+				  int up)
+{
+	struct snd_ff *ff = substream->rmidi->private_data;
+
+	guard(spinlock_irqsave)(&ff->lock);
+
+	if (up || !ff->rx_midi_error[substream->number])
+		schedule_work(&ff->rx_midi_work[substream->number]);
+}
+
+static void set_midi_substream_names(struct snd_rawmidi_str *stream,
+				     const char *const name)
+{
+	struct snd_rawmidi_substream *substream;
+
+	list_for_each_entry(substream, &stream->substreams, list) {
+		scnprintf(substream->name, sizeof(substream->name),
+			  "%s MIDI %d", name, substream->number + 1);
+	}
+}
+
+int snd_ff_create_midi_devices(struct snd_ff *ff)
+{
+	static const struct snd_rawmidi_ops midi_capture_ops = {
+		.open		= midi_capture_open,
+		.close		= midi_capture_close,
+		.trigger	= midi_capture_trigger,
+	};
+	static const struct snd_rawmidi_ops midi_playback_ops = {
+		.open		= midi_playback_open,
+		.close		= midi_playback_close,
+		.trigger	= midi_playback_trigger,
+	};
+	struct snd_rawmidi *rmidi;
+	struct snd_rawmidi_str *stream;
+	int err;
+
+	err = snd_rawmidi_new(ff->card, ff->card->driver, 0,
+			      ff->spec->midi_out_ports, ff->spec->midi_in_ports,
+			      &rmidi);
+	if (err < 0)
+		return err;
+
+	snprintf(rmidi->name, sizeof(rmidi->name),
+		 "%s MIDI", ff->card->shortname);
+	rmidi->private_data = ff;
+
+	rmidi->info_flags |= SNDRV_RAWMIDI_INFO_INPUT;
+	snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_INPUT,
+			    &midi_capture_ops);
+	stream = &rmidi->streams[SNDRV_RAWMIDI_STREAM_INPUT];
+	set_midi_substream_names(stream, ff->card->shortname);
+
+	rmidi->info_flags |= SNDRV_RAWMIDI_INFO_OUTPUT;
+	snd_rawmidi_set_ops(rmidi, SNDRV_RAWMIDI_STREAM_OUTPUT,
+			    &midi_playback_ops);
+	stream = &rmidi->streams[SNDRV_RAWMIDI_STREAM_OUTPUT];
+	set_midi_substream_names(stream, ff->card->shortname);
+
+	rmidi->info_flags |= SNDRV_RAWMIDI_INFO_DUPLEX;
+
+	return 0;
+}