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, 107 insertions, 0 deletions

diff --git a/sound/usb/power.c b/sound/usb/power.c
new file mode 100644
index 000000000..c2d708c87
--- /dev/null
+++ b/sound/usb/power.c
@@ -0,0 +1,107 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *   UAC3 Power Domain state management functions
+ */
+
+#include <linux/slab.h>
+#include <linux/usb.h>
+#include <linux/usb/audio.h>
+#include <linux/usb/audio-v2.h>
+#include <linux/usb/audio-v3.h>
+
+#include "usbaudio.h"
+#include "helper.h"
+#include "power.h"
+
+struct snd_usb_power_domain *
+snd_usb_find_power_domain(struct usb_host_interface *ctrl_iface,
+			  unsigned char id)
+{
+	struct snd_usb_power_domain *pd;
+	void *p;
+
+	pd = kzalloc_obj(*pd);
+	if (!pd)
+		return NULL;
+
+	p = NULL;
+	while ((p = snd_usb_find_csint_desc(ctrl_iface->extra,
+					    ctrl_iface->extralen,
+					    p, UAC3_POWER_DOMAIN)) != NULL) {
+		struct uac3_power_domain_descriptor *pd_desc = p;
+		int i;
+
+		if (!snd_usb_validate_audio_desc(p, UAC_VERSION_3))
+			continue;
+		for (i = 0; i < pd_desc->bNrEntities; i++) {
+			if (pd_desc->baEntityID[i] == id) {
+				pd->pd_id = pd_desc->bPowerDomainID;
+				pd->pd_d1d0_rec =
+					le16_to_cpu(pd_desc->waRecoveryTime1);
+				pd->pd_d2d0_rec =
+					le16_to_cpu(pd_desc->waRecoveryTime2);
+				pd->ctrl_iface = ctrl_iface;
+				return pd;
+			}
+		}
+	}
+
+	kfree(pd);
+	return NULL;
+}
+
+int snd_usb_power_domain_set(struct snd_usb_audio *chip,
+			     struct snd_usb_power_domain *pd,
+			     unsigned char state)
+{
+	struct usb_device *dev = chip->dev;
+	unsigned char current_state;
+	int err, idx;
+
+	idx = snd_usb_ctrl_intf(pd->ctrl_iface) | (pd->pd_id << 8);
+
+	err = snd_usb_ctl_msg(chip->dev, usb_rcvctrlpipe(chip->dev, 0),
+			      UAC2_CS_CUR,
+			      USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_IN,
+			      UAC3_AC_POWER_DOMAIN_CONTROL << 8, idx,
+			      &current_state, sizeof(current_state));
+	if (err < 0) {
+		dev_err(&dev->dev, "Can't get UAC3 power state for id %d\n",
+			pd->pd_id);
+		return err;
+	}
+
+	if (current_state == state) {
+		dev_dbg(&dev->dev, "UAC3 power domain id %d already in state %d\n",
+			pd->pd_id, state);
+		return 0;
+	}
+
+	err = snd_usb_ctl_msg(chip->dev, usb_sndctrlpipe(chip->dev, 0), UAC2_CS_CUR,
+			      USB_RECIP_INTERFACE | USB_TYPE_CLASS | USB_DIR_OUT,
+			      UAC3_AC_POWER_DOMAIN_CONTROL << 8, idx,
+			      &state, sizeof(state));
+	if (err < 0) {
+		dev_err(&dev->dev, "Can't set UAC3 power state to %d for id %d\n",
+			state, pd->pd_id);
+		return err;
+	}
+
+	if (state == UAC3_PD_STATE_D0) {
+		switch (current_state) {
+		case UAC3_PD_STATE_D2:
+			udelay(pd->pd_d2d0_rec * 50);
+			break;
+		case UAC3_PD_STATE_D1:
+			udelay(pd->pd_d1d0_rec * 50);
+			break;
+		default:
+			return -EINVAL;
+		}
+	}
+
+	dev_dbg(&dev->dev, "UAC3 power domain id %d change to state %d\n",
+		pd->pd_id, state);
+
+	return 0;
+}