ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 226 insertions, 0 deletions

diff --git a/drivers/net/wireguard/peerlookup.c b/drivers/net/wireguard/peerlookup.c
new file mode 100644
index 000000000..99651a86a
--- /dev/null
+++ b/drivers/net/wireguard/peerlookup.c
@@ -0,0 +1,226 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+#include "peerlookup.h"
+#include "peer.h"
+#include "noise.h"
+
+static struct hlist_head *pubkey_bucket(struct pubkey_hashtable *table,
+					const u8 pubkey[NOISE_PUBLIC_KEY_LEN])
+{
+	/* siphash gives us a secure 64bit number based on a random key. Since
+	 * the bits are uniformly distributed, we can then mask off to get the
+	 * bits we need.
+	 */
+	const u64 hash = siphash(pubkey, NOISE_PUBLIC_KEY_LEN, &table->key);
+
+	return &table->hashtable[hash & (HASH_SIZE(table->hashtable) - 1)];
+}
+
+struct pubkey_hashtable *wg_pubkey_hashtable_alloc(void)
+{
+	struct pubkey_hashtable *table = kvmalloc_obj(*table);
+
+	if (!table)
+		return NULL;
+
+	get_random_bytes(&table->key, sizeof(table->key));
+	hash_init(table->hashtable);
+	mutex_init(&table->lock);
+	return table;
+}
+
+void wg_pubkey_hashtable_add(struct pubkey_hashtable *table,
+			     struct wg_peer *peer)
+{
+	mutex_lock(&table->lock);
+	hlist_add_head_rcu(&peer->pubkey_hash,
+			   pubkey_bucket(table, peer->handshake.remote_static));
+	mutex_unlock(&table->lock);
+}
+
+void wg_pubkey_hashtable_remove(struct pubkey_hashtable *table,
+				struct wg_peer *peer)
+{
+	mutex_lock(&table->lock);
+	hlist_del_init_rcu(&peer->pubkey_hash);
+	mutex_unlock(&table->lock);
+}
+
+/* Returns a strong reference to a peer */
+struct wg_peer *
+wg_pubkey_hashtable_lookup(struct pubkey_hashtable *table,
+			   const u8 pubkey[NOISE_PUBLIC_KEY_LEN])
+{
+	struct wg_peer *iter_peer, *peer = NULL;
+
+	rcu_read_lock_bh();
+	hlist_for_each_entry_rcu_bh(iter_peer, pubkey_bucket(table, pubkey),
+				    pubkey_hash) {
+		if (!memcmp(pubkey, iter_peer->handshake.remote_static,
+			    NOISE_PUBLIC_KEY_LEN)) {
+			peer = iter_peer;
+			break;
+		}
+	}
+	peer = wg_peer_get_maybe_zero(peer);
+	rcu_read_unlock_bh();
+	return peer;
+}
+
+static struct hlist_head *index_bucket(struct index_hashtable *table,
+				       const __le32 index)
+{
+	/* Since the indices are random and thus all bits are uniformly
+	 * distributed, we can find its bucket simply by masking.
+	 */
+	return &table->hashtable[(__force u32)index &
+				 (HASH_SIZE(table->hashtable) - 1)];
+}
+
+struct index_hashtable *wg_index_hashtable_alloc(void)
+{
+	struct index_hashtable *table = kvmalloc_obj(*table);
+
+	if (!table)
+		return NULL;
+
+	hash_init(table->hashtable);
+	spin_lock_init(&table->lock);
+	return table;
+}
+
+/* At the moment, we limit ourselves to 2^20 total peers, which generally might
+ * amount to 2^20*3 items in this hashtable. The algorithm below works by
+ * picking a random number and testing it. We can see that these limits mean we
+ * usually succeed pretty quickly:
+ *
+ * >>> def calculation(tries, size):
+ * ...     return (size / 2**32)**(tries - 1) *  (1 - (size / 2**32))
+ * ...
+ * >>> calculation(1, 2**20 * 3)
+ * 0.999267578125
+ * >>> calculation(2, 2**20 * 3)
+ * 0.0007318854331970215
+ * >>> calculation(3, 2**20 * 3)
+ * 5.360489012673497e-07
+ * >>> calculation(4, 2**20 * 3)
+ * 3.9261394135792216e-10
+ *
+ * At the moment, we don't do any masking, so this algorithm isn't exactly
+ * constant time in either the random guessing or in the hash list lookup. We
+ * could require a minimum of 3 tries, which would successfully mask the
+ * guessing. this would not, however, help with the growing hash lengths, which
+ * is another thing to consider moving forward.
+ */
+
+__le32 wg_index_hashtable_insert(struct index_hashtable *table,
+				 struct index_hashtable_entry *entry)
+{
+	struct index_hashtable_entry *existing_entry;
+
+	spin_lock_bh(&table->lock);
+	hlist_del_init_rcu(&entry->index_hash);
+	spin_unlock_bh(&table->lock);
+
+	rcu_read_lock_bh();
+
+search_unused_slot:
+	/* First we try to find an unused slot, randomly, while unlocked. */
+	entry->index = (__force __le32)get_random_u32();
+	hlist_for_each_entry_rcu_bh(existing_entry,
+				    index_bucket(table, entry->index),
+				    index_hash) {
+		if (existing_entry->index == entry->index)
+			/* If it's already in use, we continue searching. */
+			goto search_unused_slot;
+	}
+
+	/* Once we've found an unused slot, we lock it, and then double-check
+	 * that nobody else stole it from us.
+	 */
+	spin_lock_bh(&table->lock);
+	hlist_for_each_entry_rcu_bh(existing_entry,
+				    index_bucket(table, entry->index),
+				    index_hash) {
+		if (existing_entry->index == entry->index) {
+			spin_unlock_bh(&table->lock);
+			/* If it was stolen, we start over. */
+			goto search_unused_slot;
+		}
+	}
+	/* Otherwise, we know we have it exclusively (since we're locked),
+	 * so we insert.
+	 */
+	hlist_add_head_rcu(&entry->index_hash,
+			   index_bucket(table, entry->index));
+	spin_unlock_bh(&table->lock);
+
+	rcu_read_unlock_bh();
+
+	return entry->index;
+}
+
+bool wg_index_hashtable_replace(struct index_hashtable *table,
+				struct index_hashtable_entry *old,
+				struct index_hashtable_entry *new)
+{
+	bool ret;
+
+	spin_lock_bh(&table->lock);
+	ret = !hlist_unhashed(&old->index_hash);
+	if (unlikely(!ret))
+		goto out;
+
+	new->index = old->index;
+	hlist_replace_rcu(&old->index_hash, &new->index_hash);
+
+	/* Calling init here NULLs out index_hash, and in fact after this
+	 * function returns, it's theoretically possible for this to get
+	 * reinserted elsewhere. That means the RCU lookup below might either
+	 * terminate early or jump between buckets, in which case the packet
+	 * simply gets dropped, which isn't terrible.
+	 */
+	INIT_HLIST_NODE(&old->index_hash);
+out:
+	spin_unlock_bh(&table->lock);
+	return ret;
+}
+
+void wg_index_hashtable_remove(struct index_hashtable *table,
+			       struct index_hashtable_entry *entry)
+{
+	spin_lock_bh(&table->lock);
+	hlist_del_init_rcu(&entry->index_hash);
+	spin_unlock_bh(&table->lock);
+}
+
+/* Returns a strong reference to a entry->peer */
+struct index_hashtable_entry *
+wg_index_hashtable_lookup(struct index_hashtable *table,
+			  const enum index_hashtable_type type_mask,
+			  const __le32 index, struct wg_peer **peer)
+{
+	struct index_hashtable_entry *iter_entry, *entry = NULL;
+
+	rcu_read_lock_bh();
+	hlist_for_each_entry_rcu_bh(iter_entry, index_bucket(table, index),
+				    index_hash) {
+		if (iter_entry->index == index) {
+			if (likely(iter_entry->type & type_mask))
+				entry = iter_entry;
+			break;
+		}
+	}
+	if (likely(entry)) {
+		entry->peer = wg_peer_get_maybe_zero(entry->peer);
+		if (likely(entry->peer))
+			*peer = entry->peer;
+		else
+			entry = NULL;
+	}
+	rcu_read_unlock_bh();
+	return entry;
+}