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, 86 insertions, 0 deletions

diff --git a/net/batman-adv/hash.c b/net/batman-adv/hash.c
new file mode 100644
index 000000000..b9a652bd5
--- /dev/null
+++ b/net/batman-adv/hash.c
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (C) B.A.T.M.A.N. contributors:
+ *
+ * Simon Wunderlich, Marek Lindner
+ */
+
+#include "hash.h"
+#include "main.h"
+
+#include <linux/gfp.h>
+#include <linux/lockdep.h>
+#include <linux/slab.h>
+
+/**
+ * batadv_hash_init() - clear all buckets of a hashtable
+ * @hash: hashtable to clear
+ */
+static void batadv_hash_init(struct batadv_hashtable *hash)
+{
+	u32 i;
+
+	for (i = 0; i < hash->size; i++) {
+		INIT_HLIST_HEAD(&hash->table[i]);
+		spin_lock_init(&hash->list_locks[i]);
+	}
+
+	atomic_set(&hash->generation, 0);
+}
+
+/**
+ * batadv_hash_destroy() - Free only the hashtable and the hash itself
+ * @hash: hash object to destroy
+ */
+void batadv_hash_destroy(struct batadv_hashtable *hash)
+{
+	kfree(hash->list_locks);
+	kfree(hash->table);
+	kfree(hash);
+}
+
+/**
+ * batadv_hash_new() - Allocates and clears the hashtable
+ * @size: number of hash buckets to allocate
+ *
+ * Return: newly allocated hashtable, NULL on errors
+ */
+struct batadv_hashtable *batadv_hash_new(u32 size)
+{
+	struct batadv_hashtable *hash;
+
+	hash = kmalloc_obj(*hash, GFP_ATOMIC);
+	if (!hash)
+		return NULL;
+
+	hash->table = kmalloc_objs(*hash->table, size, GFP_ATOMIC);
+	if (!hash->table)
+		goto free_hash;
+
+	hash->list_locks = kmalloc_objs(*hash->list_locks, size, GFP_ATOMIC);
+	if (!hash->list_locks)
+		goto free_table;
+
+	hash->size = size;
+	batadv_hash_init(hash);
+	return hash;
+
+free_table:
+	kfree(hash->table);
+free_hash:
+	kfree(hash);
+	return NULL;
+}
+
+/**
+ * batadv_hash_set_lock_class() - Set specific lockdep class for hash spinlocks
+ * @hash: hash object to modify
+ * @key: lockdep class key address
+ */
+void batadv_hash_set_lock_class(struct batadv_hashtable *hash,
+				struct lock_class_key *key)
+{
+	u32 i;
+
+	for (i = 0; i < hash->size; i++)
+		lockdep_set_class(&hash->list_locks[i], key);
+}