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, 94 insertions, 0 deletions

diff --git a/fs/smb/client/netlink.c b/fs/smb/client/netlink.c
new file mode 100644
index 000000000..0dd10913c
--- /dev/null
+++ b/fs/smb/client/netlink.c
@@ -0,0 +1,94 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Netlink routines for CIFS
+ *
+ * Copyright (c) 2020 Samuel Cabrero <scabrero@suse.de>
+ */
+
+#include <net/genetlink.h>
+#include <uapi/linux/cifs/cifs_netlink.h>
+
+#include "netlink.h"
+#include "cifsglob.h"
+#include "cifs_debug.h"
+#include "cifs_swn.h"
+
+static const struct nla_policy cifs_genl_policy[CIFS_GENL_ATTR_MAX + 1] = {
+	[CIFS_GENL_ATTR_SWN_REGISTRATION_ID]	= { .type = NLA_U32 },
+	[CIFS_GENL_ATTR_SWN_NET_NAME]		= { .type = NLA_STRING },
+	[CIFS_GENL_ATTR_SWN_SHARE_NAME]		= { .type = NLA_STRING },
+	[CIFS_GENL_ATTR_SWN_IP]			= { .len = sizeof(struct sockaddr_storage) },
+	[CIFS_GENL_ATTR_SWN_NET_NAME_NOTIFY]	= { .type = NLA_FLAG },
+	[CIFS_GENL_ATTR_SWN_SHARE_NAME_NOTIFY]	= { .type = NLA_FLAG },
+	[CIFS_GENL_ATTR_SWN_IP_NOTIFY]		= { .type = NLA_FLAG },
+	[CIFS_GENL_ATTR_SWN_KRB_AUTH]		= { .type = NLA_FLAG },
+	[CIFS_GENL_ATTR_SWN_USER_NAME]		= { .type = NLA_STRING },
+	[CIFS_GENL_ATTR_SWN_PASSWORD]		= { .type = NLA_STRING },
+	[CIFS_GENL_ATTR_SWN_DOMAIN_NAME]	= { .type = NLA_STRING },
+	[CIFS_GENL_ATTR_SWN_NOTIFICATION_TYPE]	= { .type = NLA_U32 },
+	[CIFS_GENL_ATTR_SWN_RESOURCE_STATE]	= { .type = NLA_U32 },
+	[CIFS_GENL_ATTR_SWN_RESOURCE_NAME]	= { .type = NLA_STRING},
+};
+
+static const struct genl_ops cifs_genl_ops[] = {
+	{
+		.cmd = CIFS_GENL_CMD_SWN_NOTIFY,
+		.flags = GENL_ADMIN_PERM,
+		.validate = GENL_DONT_VALIDATE_STRICT | GENL_DONT_VALIDATE_DUMP,
+		.doit = cifs_swn_notify,
+	},
+};
+
+static const struct genl_multicast_group cifs_genl_mcgrps[] = {
+	[CIFS_GENL_MCGRP_SWN] = {
+		.name = CIFS_GENL_MCGRP_SWN_NAME,
+		.flags = GENL_MCAST_CAP_NET_ADMIN,
+	},
+};
+
+struct genl_family cifs_genl_family = {
+	.name		= CIFS_GENL_NAME,
+	.version	= CIFS_GENL_VERSION,
+	.hdrsize	= 0,
+	.maxattr	= CIFS_GENL_ATTR_MAX,
+	.module		= THIS_MODULE,
+	.policy		= cifs_genl_policy,
+	.ops		= cifs_genl_ops,
+	.n_ops		= ARRAY_SIZE(cifs_genl_ops),
+	.resv_start_op	= CIFS_GENL_CMD_SWN_NOTIFY + 1,
+	.mcgrps		= cifs_genl_mcgrps,
+	.n_mcgrps	= ARRAY_SIZE(cifs_genl_mcgrps),
+};
+
+/**
+ * cifs_genl_init - Register generic netlink family
+ *
+ * Return zero if initialized successfully, otherwise non-zero.
+ */
+int cifs_genl_init(void)
+{
+	int ret;
+
+	ret = genl_register_family(&cifs_genl_family);
+	if (ret < 0) {
+		cifs_dbg(VFS, "%s: failed to register netlink family\n",
+				__func__);
+		return ret;
+	}
+
+	return 0;
+}
+
+/**
+ * cifs_genl_exit - Unregister generic netlink family
+ */
+void cifs_genl_exit(void)
+{
+	int ret;
+
+	ret = genl_unregister_family(&cifs_genl_family);
+	if (ret < 0) {
+		cifs_dbg(VFS, "%s: failed to unregister netlink family\n",
+				__func__);
+	}
+}