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, 114 insertions, 0 deletions

diff --git a/include/net/scm.h b/include/net/scm.h
new file mode 100644
index 000000000..86ae6bc10
--- /dev/null
+++ b/include/net/scm.h
@@ -0,0 +1,114 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __LINUX_NET_SCM_H
+#define __LINUX_NET_SCM_H
+
+#include <linux/limits.h>
+#include <linux/net.h>
+#include <linux/cred.h>
+#include <linux/file.h>
+#include <linux/security.h>
+#include <linux/pid.h>
+#include <linux/nsproxy.h>
+#include <linux/sched/signal.h>
+#include <net/compat.h>
+
+/* Well, we should have at least one descriptor open
+ * to accept passed FDs 8)
+ */
+#define SCM_MAX_FD	253
+
+struct scm_creds {
+	u32	pid;
+	kuid_t	uid;
+	kgid_t	gid;
+};
+
+#ifdef CONFIG_UNIX
+struct unix_edge;
+#endif
+
+struct scm_fp_list {
+	short			count;
+	short			count_unix;
+	short			max;
+#ifdef CONFIG_UNIX
+	bool			inflight;
+	bool			dead;
+	struct list_head	vertices;
+	struct unix_edge	*edges;
+#endif
+	struct user_struct	*user;
+	struct file		*fp[SCM_MAX_FD];
+};
+
+struct scm_cookie {
+	struct pid		*pid;		/* Skb credentials */
+	struct scm_fp_list	*fp;		/* Passed files		*/
+	struct scm_creds	creds;		/* Skb credentials	*/
+#ifdef CONFIG_SECURITY_NETWORK
+	u32			secid;		/* Passed security ID 	*/
+#endif
+};
+
+void scm_detach_fds(struct msghdr *msg, struct scm_cookie *scm, bool notrunc);
+void scm_detach_fds_compat(struct msghdr *msg, struct scm_cookie *scm, bool notrunc);
+int __scm_send(struct socket *sock, struct msghdr *msg, struct scm_cookie *scm);
+void __scm_destroy(struct scm_cookie *scm);
+struct scm_fp_list *scm_fp_dup(struct scm_fp_list *fpl);
+
+#ifdef CONFIG_SECURITY_NETWORK
+static __inline__ void unix_get_peersec_dgram(struct socket *sock, struct scm_cookie *scm)
+{
+	security_socket_getpeersec_dgram(sock, NULL, &scm->secid);
+}
+#else
+static __inline__ void unix_get_peersec_dgram(struct socket *sock, struct scm_cookie *scm)
+{ }
+#endif /* CONFIG_SECURITY_NETWORK */
+
+static __inline__ void scm_set_cred(struct scm_cookie *scm,
+				    struct pid *pid, kuid_t uid, kgid_t gid)
+{
+	scm->pid = get_pid(pid);
+	scm->creds.pid = pid_vnr(pid);
+	scm->creds.uid = uid;
+	scm->creds.gid = gid;
+}
+
+static __inline__ void scm_destroy_cred(struct scm_cookie *scm)
+{
+	put_pid(scm->pid);
+	scm->pid = NULL;
+}
+
+static __inline__ void scm_destroy(struct scm_cookie *scm)
+{
+	scm_destroy_cred(scm);
+	if (scm->fp)
+		__scm_destroy(scm);
+}
+
+static __inline__ int scm_send(struct socket *sock, struct msghdr *msg,
+			       struct scm_cookie *scm, bool forcecreds)
+{
+	memset(scm, 0, sizeof(*scm));
+	scm->creds.uid = INVALID_UID;
+	scm->creds.gid = INVALID_GID;
+	if (forcecreds)
+		scm_set_cred(scm, task_tgid(current), current_uid(), current_gid());
+	unix_get_peersec_dgram(sock, scm);
+	if (msg->msg_controllen <= 0)
+		return 0;
+	return __scm_send(sock, msg, scm);
+}
+
+void scm_recv(struct socket *sock, struct msghdr *msg,
+	      struct scm_cookie *scm, int flags);
+void scm_recv_unix(struct socket *sock, struct msghdr *msg,
+		   struct scm_cookie *scm, int flags);
+
+int scm_recv_one_fd(struct file *f, int __user *ufd, unsigned int flags,
+		    bool notrunc);
+
+#endif /* __LINUX_NET_SCM_H */
+