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, 64 insertions, 0 deletions

diff --git a/include/net/af_unix.h b/include/net/af_unix.h
new file mode 100644
index 000000000..bb1b3dee0
--- /dev/null
+++ b/include/net/af_unix.h
@@ -0,0 +1,64 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_NET_AFUNIX_H
+#define __LINUX_NET_AFUNIX_H
+
+#include <linux/atomic.h>
+#include <linux/mutex.h>
+#include <linux/net.h>
+#include <linux/path.h>
+#include <linux/refcount.h>
+#include <linux/spinlock.h>
+#include <linux/wait.h>
+#include <net/sock.h>
+#include <uapi/linux/un.h>
+
+#if IS_ENABLED(CONFIG_UNIX)
+struct unix_sock *unix_get_socket(struct file *filp);
+#else
+static inline struct unix_sock *unix_get_socket(struct file *filp)
+{
+	return NULL;
+}
+#endif
+
+struct unix_address {
+	refcount_t	refcnt;
+	int		len;
+	struct sockaddr_un name[];
+};
+
+struct scm_stat {
+	atomic_t nr_fds;
+	unsigned long nr_unix_fds;
+};
+
+/* The AF_UNIX socket */
+struct unix_sock {
+	/* WARNING: sk has to be the first member */
+	struct sock		sk;
+	struct unix_address	*addr;
+	struct path		path;
+	struct mutex		iolock, bindlock;
+	struct sock		*peer;
+	struct sock		*listener;
+	struct unix_vertex	*vertex;
+	spinlock_t		lock;
+	struct socket_wq	peer_wq;
+#define peer_wait		peer_wq.wait
+	wait_queue_entry_t	peer_wake;
+	struct scm_stat		scm_stat;
+	int			inq_len;
+	bool			recvmsg_inq;
+	bool			scm_rights_notrunc;
+#if IS_ENABLED(CONFIG_AF_UNIX_OOB)
+	struct sk_buff		*oob_skb;
+#endif
+};
+
+#define unix_sk(ptr) container_of_const(ptr, struct unix_sock, sk)
+#define unix_peer(sk) (unix_sk(sk)->peer)
+
+#define unix_state_lock(s)	spin_lock(&unix_sk(s)->lock)
+#define unix_state_unlock(s)	spin_unlock(&unix_sk(s)->lock)
+
+#endif