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, 334 insertions, 0 deletions

diff --git a/ipc/ipc_sysctl.c b/ipc/ipc_sysctl.c
new file mode 100644
index 000000000..9b087ebeb
--- /dev/null
+++ b/ipc/ipc_sysctl.c
@@ -0,0 +1,334 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  Copyright (C) 2007
+ *
+ *  Author: Eric Biederman <ebiederm@xmision.com>
+ */
+
+#include <linux/module.h>
+#include <linux/ipc.h>
+#include <linux/nsproxy.h>
+#include <linux/sysctl.h>
+#include <linux/uaccess.h>
+#include <linux/capability.h>
+#include <linux/ipc_namespace.h>
+#include <linux/msg.h>
+#include <linux/slab.h>
+#include <linux/cred.h>
+#include "util.h"
+
+static int proc_ipc_dointvec_minmax_orphans(const struct ctl_table *table, int write,
+		void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct ipc_namespace *ns =
+		container_of(table->data, struct ipc_namespace, shm_rmid_forced);
+	int err;
+
+	err = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+
+	if (err < 0)
+		return err;
+	if (ns->shm_rmid_forced)
+		shm_destroy_orphaned(ns);
+	return err;
+}
+
+static int proc_ipc_auto_msgmni(const struct ctl_table *table, int write,
+		void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct ctl_table ipc_table;
+	int dummy = 0;
+
+	memcpy(&ipc_table, table, sizeof(ipc_table));
+	ipc_table.data = &dummy;
+
+	if (write)
+		pr_info_once("writing to auto_msgmni has no effect");
+
+	return proc_dointvec_minmax(&ipc_table, write, buffer, lenp, ppos);
+}
+
+static int proc_ipc_sem_dointvec(const struct ctl_table *table, int write,
+	void *buffer, size_t *lenp, loff_t *ppos)
+{
+	struct ipc_namespace *ns =
+		container_of(table->data, struct ipc_namespace, sem_ctls);
+	int ret, semmni;
+
+	semmni = ns->sem_ctls[3];
+	ret = proc_dointvec(table, write, buffer, lenp, ppos);
+
+	if (!ret)
+		ret = sem_check_semmni(ns);
+
+	/*
+	 * Reset the semmni value if an error happens.
+	 */
+	if (ret)
+		ns->sem_ctls[3] = semmni;
+	return ret;
+}
+
+int ipc_mni = IPCMNI;
+int ipc_mni_shift = IPCMNI_SHIFT;
+int ipc_min_cycle = RADIX_TREE_MAP_SIZE;
+
+static const struct ctl_table ipc_sysctls[] = {
+	{
+		.procname	= "shmmax",
+		.data		= &init_ipc_ns.shm_ctlmax,
+		.maxlen		= sizeof(init_ipc_ns.shm_ctlmax),
+		.mode		= 0644,
+		.proc_handler	= proc_doulongvec_minmax,
+	},
+	{
+		.procname	= "shmall",
+		.data		= &init_ipc_ns.shm_ctlall,
+		.maxlen		= sizeof(init_ipc_ns.shm_ctlall),
+		.mode		= 0644,
+		.proc_handler	= proc_doulongvec_minmax,
+	},
+	{
+		.procname	= "shmmni",
+		.data		= &init_ipc_ns.shm_ctlmni,
+		.maxlen		= sizeof(init_ipc_ns.shm_ctlmni),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= &ipc_mni,
+	},
+	{
+		.procname	= "shm_rmid_forced",
+		.data		= &init_ipc_ns.shm_rmid_forced,
+		.maxlen		= sizeof(init_ipc_ns.shm_rmid_forced),
+		.mode		= 0644,
+		.proc_handler	= proc_ipc_dointvec_minmax_orphans,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+	{
+		.procname	= "msgmax",
+		.data		= &init_ipc_ns.msg_ctlmax,
+		.maxlen		= sizeof(init_ipc_ns.msg_ctlmax),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_INT_MAX,
+	},
+	{
+		.procname	= "msgmni",
+		.data		= &init_ipc_ns.msg_ctlmni,
+		.maxlen		= sizeof(init_ipc_ns.msg_ctlmni),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= &ipc_mni,
+	},
+	{
+		.procname	= "auto_msgmni",
+		.data		= NULL,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_ipc_auto_msgmni,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_ONE,
+	},
+	{
+		.procname	=  "msgmnb",
+		.data		= &init_ipc_ns.msg_ctlmnb,
+		.maxlen		= sizeof(init_ipc_ns.msg_ctlmnb),
+		.mode		= 0644,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_INT_MAX,
+	},
+	{
+		.procname	= "sem",
+		.data		= &init_ipc_ns.sem_ctls,
+		.maxlen		= 4*sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= proc_ipc_sem_dointvec,
+	},
+#ifdef CONFIG_CHECKPOINT_RESTORE
+	{
+		.procname	= "sem_next_id",
+		.data		= &init_ipc_ns.ids[IPC_SEM_IDS].next_id,
+		.maxlen		= sizeof(init_ipc_ns.ids[IPC_SEM_IDS].next_id),
+		.mode		= 0444,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_INT_MAX,
+	},
+	{
+		.procname	= "msg_next_id",
+		.data		= &init_ipc_ns.ids[IPC_MSG_IDS].next_id,
+		.maxlen		= sizeof(init_ipc_ns.ids[IPC_MSG_IDS].next_id),
+		.mode		= 0444,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_INT_MAX,
+	},
+	{
+		.procname	= "shm_next_id",
+		.data		= &init_ipc_ns.ids[IPC_SHM_IDS].next_id,
+		.maxlen		= sizeof(init_ipc_ns.ids[IPC_SHM_IDS].next_id),
+		.mode		= 0444,
+		.proc_handler	= proc_dointvec_minmax,
+		.extra1		= SYSCTL_ZERO,
+		.extra2		= SYSCTL_INT_MAX,
+	},
+#endif
+};
+
+static struct ctl_table_set *set_lookup(struct ctl_table_root *root)
+{
+	return &current->nsproxy->ipc_ns->ipc_set;
+}
+
+static int set_is_seen(struct ctl_table_set *set)
+{
+	return &current->nsproxy->ipc_ns->ipc_set == set;
+}
+
+static void ipc_set_ownership(struct ctl_table_header *head,
+			      kuid_t *uid, kgid_t *gid)
+{
+	struct ipc_namespace *ns =
+		container_of(head->set, struct ipc_namespace, ipc_set);
+
+	kuid_t ns_root_uid = make_kuid(ns->user_ns, 0);
+	kgid_t ns_root_gid = make_kgid(ns->user_ns, 0);
+
+	*uid = uid_valid(ns_root_uid) ? ns_root_uid : GLOBAL_ROOT_UID;
+	*gid = gid_valid(ns_root_gid) ? ns_root_gid : GLOBAL_ROOT_GID;
+}
+
+static int ipc_permissions(struct ctl_table_header *head, const struct ctl_table *table)
+{
+	int mode = table->mode;
+
+#ifdef CONFIG_CHECKPOINT_RESTORE
+	struct ipc_namespace *ns =
+		container_of(head->set, struct ipc_namespace, ipc_set);
+
+	if (((table->data == &ns->ids[IPC_SEM_IDS].next_id) ||
+	     (table->data == &ns->ids[IPC_MSG_IDS].next_id) ||
+	     (table->data == &ns->ids[IPC_SHM_IDS].next_id)) &&
+	    checkpoint_restore_ns_capable_noaudit(ns->user_ns))
+		mode = 0666;
+	else
+#endif
+	{
+		kuid_t ns_root_uid;
+		kgid_t ns_root_gid;
+
+		ipc_set_ownership(head, &ns_root_uid, &ns_root_gid);
+
+		if (uid_eq(current_euid(), ns_root_uid))
+			mode >>= 6;
+
+		else if (in_egroup_p(ns_root_gid))
+			mode >>= 3;
+	}
+
+	mode &= 7;
+
+	return (mode << 6) | (mode << 3) | mode;
+}
+
+static struct ctl_table_root set_root = {
+	.lookup = set_lookup,
+	.permissions = ipc_permissions,
+	.set_ownership = ipc_set_ownership,
+};
+
+bool setup_ipc_sysctls(struct ipc_namespace *ns)
+{
+	struct ctl_table *tbl;
+
+	setup_sysctl_set(&ns->ipc_set, &set_root, set_is_seen);
+
+	tbl = kmemdup(ipc_sysctls, sizeof(ipc_sysctls), GFP_KERNEL);
+	if (tbl) {
+		int i;
+
+		for (i = 0; i < ARRAY_SIZE(ipc_sysctls); i++) {
+			if (tbl[i].data == &init_ipc_ns.shm_ctlmax)
+				tbl[i].data = &ns->shm_ctlmax;
+
+			else if (tbl[i].data == &init_ipc_ns.shm_ctlall)
+				tbl[i].data = &ns->shm_ctlall;
+
+			else if (tbl[i].data == &init_ipc_ns.shm_ctlmni)
+				tbl[i].data = &ns->shm_ctlmni;
+
+			else if (tbl[i].data == &init_ipc_ns.shm_rmid_forced)
+				tbl[i].data = &ns->shm_rmid_forced;
+
+			else if (tbl[i].data == &init_ipc_ns.msg_ctlmax)
+				tbl[i].data = &ns->msg_ctlmax;
+
+			else if (tbl[i].data == &init_ipc_ns.msg_ctlmni)
+				tbl[i].data = &ns->msg_ctlmni;
+
+			else if (tbl[i].data == &init_ipc_ns.msg_ctlmnb)
+				tbl[i].data = &ns->msg_ctlmnb;
+
+			else if (tbl[i].data == &init_ipc_ns.sem_ctls)
+				tbl[i].data = &ns->sem_ctls;
+#ifdef CONFIG_CHECKPOINT_RESTORE
+			else if (tbl[i].data == &init_ipc_ns.ids[IPC_SEM_IDS].next_id)
+				tbl[i].data = &ns->ids[IPC_SEM_IDS].next_id;
+
+			else if (tbl[i].data == &init_ipc_ns.ids[IPC_MSG_IDS].next_id)
+				tbl[i].data = &ns->ids[IPC_MSG_IDS].next_id;
+
+			else if (tbl[i].data == &init_ipc_ns.ids[IPC_SHM_IDS].next_id)
+				tbl[i].data = &ns->ids[IPC_SHM_IDS].next_id;
+#endif
+			else
+				tbl[i].data = NULL;
+		}
+
+		ns->ipc_sysctls = __register_sysctl_table(&ns->ipc_set, "kernel", tbl,
+							  ARRAY_SIZE(ipc_sysctls));
+	}
+	if (!ns->ipc_sysctls) {
+		kfree(tbl);
+		retire_sysctl_set(&ns->ipc_set);
+		return false;
+	}
+
+	return true;
+}
+
+void retire_ipc_sysctls(struct ipc_namespace *ns)
+{
+	const struct ctl_table *tbl;
+
+	tbl = ns->ipc_sysctls->ctl_table_arg;
+	unregister_sysctl_table(ns->ipc_sysctls);
+	retire_sysctl_set(&ns->ipc_set);
+	kfree(tbl);
+}
+
+static int __init ipc_sysctl_init(void)
+{
+	if (!setup_ipc_sysctls(&init_ipc_ns)) {
+		pr_warn("ipc sysctl registration failed\n");
+		return -ENOMEM;
+	}
+	return 0;
+}
+
+device_initcall(ipc_sysctl_init);
+
+static int __init ipc_mni_extend(char *str)
+{
+	ipc_mni = IPCMNI_EXTEND;
+	ipc_mni_shift = IPCMNI_EXTEND_SHIFT;
+	ipc_min_cycle = IPCMNI_EXTEND_MIN_CYCLE;
+	pr_info("IPCMNI extended to %d.\n", ipc_mni);
+	return 0;
+}
+early_param("ipcmni_extend", ipc_mni_extend);