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, 182 insertions, 0 deletions

diff --git a/crypto/sig.c b/crypto/sig.c
new file mode 100644
index 000000000..7d2048da5
--- /dev/null
+++ b/crypto/sig.c
@@ -0,0 +1,182 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Public Key Signature Algorithm
+ *
+ * Copyright (c) 2023 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+
+#include <crypto/internal/sig.h>
+#include <linux/cryptouser.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/seq_file.h>
+#include <linux/string.h>
+#include <net/netlink.h>
+
+#include "internal.h"
+
+static void crypto_sig_exit_tfm(struct crypto_tfm *tfm)
+{
+	struct crypto_sig *sig = __crypto_sig_tfm(tfm);
+	struct sig_alg *alg = crypto_sig_alg(sig);
+
+	alg->exit(sig);
+}
+
+static int crypto_sig_init_tfm(struct crypto_tfm *tfm)
+{
+	struct crypto_sig *sig = __crypto_sig_tfm(tfm);
+	struct sig_alg *alg = crypto_sig_alg(sig);
+
+	if (alg->exit)
+		sig->base.exit = crypto_sig_exit_tfm;
+
+	if (alg->init)
+		return alg->init(sig);
+
+	return 0;
+}
+
+static void crypto_sig_free_instance(struct crypto_instance *inst)
+{
+	struct sig_instance *sig = sig_instance(inst);
+
+	sig->free(sig);
+}
+
+static void __maybe_unused crypto_sig_show(struct seq_file *m,
+					   struct crypto_alg *alg)
+{
+	seq_puts(m, "type         : sig\n");
+}
+
+static int __maybe_unused crypto_sig_report(struct sk_buff *skb,
+					    struct crypto_alg *alg)
+{
+	struct crypto_report_sig rsig = {
+		.type = "sig",
+	};
+
+	return nla_put(skb, CRYPTOCFGA_REPORT_SIG, sizeof(rsig), &rsig);
+}
+
+static const struct crypto_type crypto_sig_type = {
+	.extsize = crypto_alg_extsize,
+	.init_tfm = crypto_sig_init_tfm,
+	.free = crypto_sig_free_instance,
+#ifdef CONFIG_PROC_FS
+	.show = crypto_sig_show,
+#endif
+#if IS_ENABLED(CONFIG_CRYPTO_USER)
+	.report = crypto_sig_report,
+#endif
+	.maskclear = ~CRYPTO_ALG_TYPE_MASK,
+	.maskset = CRYPTO_ALG_TYPE_MASK,
+	.type = CRYPTO_ALG_TYPE_SIG,
+	.tfmsize = offsetof(struct crypto_sig, base),
+	.algsize = offsetof(struct sig_alg, base),
+};
+
+struct crypto_sig *crypto_alloc_sig(const char *alg_name, u32 type, u32 mask)
+{
+	return crypto_alloc_tfm(alg_name, &crypto_sig_type, type, mask);
+}
+EXPORT_SYMBOL_GPL(crypto_alloc_sig);
+
+static int sig_default_sign(struct crypto_sig *tfm,
+			    const void *src, unsigned int slen,
+			    void *dst, unsigned int dlen)
+{
+	return -ENOSYS;
+}
+
+static int sig_default_verify(struct crypto_sig *tfm,
+			      const void *src, unsigned int slen,
+			      const void *dst, unsigned int dlen)
+{
+	return -ENOSYS;
+}
+
+static int sig_default_set_key(struct crypto_sig *tfm,
+			       const void *key, unsigned int keylen)
+{
+	return -ENOSYS;
+}
+
+static unsigned int sig_default_size(struct crypto_sig *tfm)
+{
+	return DIV_ROUND_UP_POW2(crypto_sig_keysize(tfm), BITS_PER_BYTE);
+}
+
+static int sig_prepare_alg(struct sig_alg *alg)
+{
+	struct crypto_alg *base = &alg->base;
+
+	if (!alg->sign)
+		alg->sign = sig_default_sign;
+	if (!alg->verify)
+		alg->verify = sig_default_verify;
+	if (!alg->set_priv_key)
+		alg->set_priv_key = sig_default_set_key;
+	if (!alg->set_pub_key)
+		return -EINVAL;
+	if (!alg->key_size)
+		return -EINVAL;
+	if (!alg->max_size)
+		alg->max_size = sig_default_size;
+	if (!alg->digest_size)
+		alg->digest_size = sig_default_size;
+
+	base->cra_type = &crypto_sig_type;
+	base->cra_flags &= ~CRYPTO_ALG_TYPE_MASK;
+	base->cra_flags |= CRYPTO_ALG_TYPE_SIG;
+
+	return 0;
+}
+
+int crypto_register_sig(struct sig_alg *alg)
+{
+	struct crypto_alg *base = &alg->base;
+	int err;
+
+	err = sig_prepare_alg(alg);
+	if (err)
+		return err;
+
+	return crypto_register_alg(base);
+}
+EXPORT_SYMBOL_GPL(crypto_register_sig);
+
+void crypto_unregister_sig(struct sig_alg *alg)
+{
+	crypto_unregister_alg(&alg->base);
+}
+EXPORT_SYMBOL_GPL(crypto_unregister_sig);
+
+int sig_register_instance(struct crypto_template *tmpl,
+			  struct sig_instance *inst)
+{
+	int err;
+
+	if (WARN_ON(!inst->free))
+		return -EINVAL;
+
+	err = sig_prepare_alg(&inst->alg);
+	if (err)
+		return err;
+
+	return crypto_register_instance(tmpl, sig_crypto_instance(inst));
+}
+EXPORT_SYMBOL_GPL(sig_register_instance);
+
+int crypto_grab_sig(struct crypto_sig_spawn *spawn,
+		    struct crypto_instance *inst,
+		    const char *name, u32 type, u32 mask)
+{
+	spawn->base.frontend = &crypto_sig_type;
+	return crypto_grab_spawn(&spawn->base, inst, name, type, mask);
+}
+EXPORT_SYMBOL_GPL(crypto_grab_sig);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("Public Key Signature Algorithms");