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, 199 insertions, 0 deletions

diff --git a/security/selinux/ss/hashtab.c b/security/selinux/ss/hashtab.c
new file mode 100644
index 000000000..9ffc8a371
--- /dev/null
+++ b/security/selinux/ss/hashtab.c
@@ -0,0 +1,199 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Implementation of the hash table type.
+ *
+ * Author : Stephen Smalley, <stephen.smalley.work@gmail.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/errno.h>
+#include "hashtab.h"
+#include "security.h"
+
+static struct kmem_cache *hashtab_node_cachep __ro_after_init;
+
+/*
+ * Here we simply round the number of elements up to the nearest power of two.
+ * I tried also other options like rounding down or rounding to the closest
+ * power of two (up or down based on which is closer), but I was unable to
+ * find any significant difference in lookup/insert performance that would
+ * justify switching to a different (less intuitive) formula. It could be that
+ * a different formula is actually more optimal, but any future changes here
+ * should be supported with performance/memory usage data.
+ *
+ * The total memory used by the htable arrays (only) with Fedora policy loaded
+ * is approximately 163 KB at the time of writing.
+ */
+static u32 hashtab_compute_size(u32 nel)
+{
+	return nel == 0 ? 0 : roundup_pow_of_two(nel);
+}
+
+int hashtab_init(struct hashtab *h, u32 nel_hint)
+{
+	u32 size = hashtab_compute_size(nel_hint);
+
+	/* should already be zeroed, but better be safe */
+	h->nel = 0;
+	h->size = 0;
+	h->htable = NULL;
+
+	if (size) {
+		h->htable = kzalloc_objs(*h->htable, size,
+					 GFP_KERNEL | __GFP_NOWARN);
+		if (!h->htable)
+			return -ENOMEM;
+		h->size = size;
+	}
+	return 0;
+}
+
+int __hashtab_insert(struct hashtab *h, struct hashtab_node **dst, void *key,
+		     void *datum)
+{
+	struct hashtab_node *newnode;
+
+	newnode = kmem_cache_zalloc(hashtab_node_cachep, GFP_KERNEL);
+	if (!newnode)
+		return -ENOMEM;
+	newnode->key = key;
+	newnode->datum = datum;
+	newnode->next = *dst;
+	*dst = newnode;
+
+	h->nel++;
+	return 0;
+}
+
+void hashtab_destroy(struct hashtab *h)
+{
+	u32 i;
+	struct hashtab_node *cur, *temp;
+
+	for (i = 0; i < h->size; i++) {
+		cur = h->htable[i];
+		while (cur) {
+			temp = cur;
+			cur = cur->next;
+			kmem_cache_free(hashtab_node_cachep, temp);
+		}
+		h->htable[i] = NULL;
+	}
+
+	kfree(h->htable);
+	h->htable = NULL;
+}
+
+int hashtab_map(struct hashtab *h, int (*apply)(void *k, void *d, void *args),
+		void *args)
+{
+	u32 i;
+	int ret;
+	struct hashtab_node *cur;
+
+	for (i = 0; i < h->size; i++) {
+		cur = h->htable[i];
+		while (cur) {
+			ret = apply(cur->key, cur->datum, args);
+			if (ret)
+				return ret;
+			cur = cur->next;
+		}
+	}
+	return 0;
+}
+
+#ifdef CONFIG_SECURITY_SELINUX_DEBUG
+void hashtab_stat(struct hashtab *h, struct hashtab_info *info)
+{
+	u32 i, chain_len, slots_used, max_chain_len;
+	u64 chain2_len_sum;
+	struct hashtab_node *cur;
+
+	slots_used = 0;
+	max_chain_len = 0;
+	chain2_len_sum = 0;
+	for (i = 0; i < h->size; i++) {
+		cur = h->htable[i];
+		if (cur) {
+			slots_used++;
+			chain_len = 0;
+			while (cur) {
+				chain_len++;
+				cur = cur->next;
+			}
+
+			if (chain_len > max_chain_len)
+				max_chain_len = chain_len;
+
+			chain2_len_sum += (u64)chain_len * chain_len;
+		}
+	}
+
+	info->slots_used = slots_used;
+	info->max_chain_len = max_chain_len;
+	info->chain2_len_sum = chain2_len_sum;
+}
+#endif /* CONFIG_SECURITY_SELINUX_DEBUG */
+
+int hashtab_duplicate(struct hashtab *new, const struct hashtab *orig,
+		      int (*copy)(struct hashtab_node *new,
+				  const struct hashtab_node *orig, void *args),
+		      int (*destroy)(void *k, void *d, void *args), void *args)
+{
+	const struct hashtab_node *orig_cur;
+	struct hashtab_node *cur, *tmp, *tail;
+	u32 i;
+	int rc;
+
+	memset(new, 0, sizeof(*new));
+
+	new->htable = kzalloc_objs(*new->htable, orig->size);
+	if (!new->htable)
+		return -ENOMEM;
+
+	new->size = orig->size;
+
+	for (i = 0; i < orig->size; i++) {
+		tail = NULL;
+		for (orig_cur = orig->htable[i]; orig_cur;
+		     orig_cur = orig_cur->next) {
+			tmp = kmem_cache_zalloc(hashtab_node_cachep,
+						GFP_KERNEL);
+			if (!tmp)
+				goto error;
+			rc = copy(tmp, orig_cur, args);
+			if (rc) {
+				kmem_cache_free(hashtab_node_cachep, tmp);
+				goto error;
+			}
+			tmp->next = NULL;
+			if (!tail)
+				new->htable[i] = tmp;
+			else
+				tail->next = tmp;
+			tail = tmp;
+			new->nel++;
+		}
+	}
+
+	return 0;
+
+error:
+	for (i = 0; i < new->size; i++) {
+		for (cur = new->htable[i]; cur; cur = tmp) {
+			tmp = cur->next;
+			destroy(cur->key, cur->datum, args);
+			kmem_cache_free(hashtab_node_cachep, cur);
+		}
+	}
+	kfree(new->htable);
+	memset(new, 0, sizeof(*new));
+	return -ENOMEM;
+}
+
+void __init hashtab_cache_init(void)
+{
+	hashtab_node_cachep = KMEM_CACHE(hashtab_node, SLAB_PANIC);
+}