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, 54 insertions, 0 deletions

diff --git a/include/net/netprio_cgroup.h b/include/net/netprio_cgroup.h
new file mode 100644
index 000000000..dec7522b6
--- /dev/null
+++ b/include/net/netprio_cgroup.h
@@ -0,0 +1,54 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * netprio_cgroup.h			Control Group Priority set
+ *
+ * Authors:	Neil Horman <nhorman@tuxdriver.com>
+ */
+
+#ifndef _NETPRIO_CGROUP_H
+#define _NETPRIO_CGROUP_H
+
+#include <linux/cgroup.h>
+#include <linux/hardirq.h>
+#include <linux/rcupdate.h>
+
+#if IS_ENABLED(CONFIG_CGROUP_NET_PRIO)
+struct netprio_map {
+	struct rcu_head rcu;
+	u32 priomap_len;
+	u32 priomap[];
+};
+
+static inline u32 task_netprioidx(struct task_struct *p)
+{
+	struct cgroup_subsys_state *css;
+	u32 idx;
+
+	rcu_read_lock();
+	css = task_css(p, net_prio_cgrp_id);
+	idx = css->id;
+	rcu_read_unlock();
+	return idx;
+}
+
+static inline void sock_update_netprioidx(struct sock_cgroup_data *skcd)
+{
+	if (in_interrupt())
+		return;
+
+	sock_cgroup_set_prioidx(skcd, task_netprioidx(current));
+}
+
+#else /* !CONFIG_CGROUP_NET_PRIO */
+
+static inline u32 task_netprioidx(struct task_struct *p)
+{
+	return 0;
+}
+
+static inline void sock_update_netprioidx(struct sock_cgroup_data *skcd)
+{
+}
+
+#endif /* CONFIG_CGROUP_NET_PRIO */
+#endif  /* _NET_CLS_CGROUP_H */