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, 56 insertions, 0 deletions

diff --git a/security/selinux/ss/symtab.c b/security/selinux/ss/symtab.c
new file mode 100644
index 000000000..a756554e7
--- /dev/null
+++ b/security/selinux/ss/symtab.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Implementation of the symbol table type.
+ *
+ * Author : Stephen Smalley, <stephen.smalley.work@gmail.com>
+ */
+
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/errno.h>
+#include "symtab.h"
+
+static unsigned int symhash(const void *key)
+{
+	/*
+	 * djb2a
+	 * Public domain from cdb v0.75
+	 */
+	unsigned int hash = 5381;
+	unsigned char c;
+
+	while ((c = *(const unsigned char *)key++))
+		hash = ((hash << 5) + hash) ^ c;
+
+	return hash;
+}
+
+static int symcmp(const void *key1, const void *key2)
+{
+	const char *keyp1, *keyp2;
+
+	keyp1 = key1;
+	keyp2 = key2;
+	return strcmp(keyp1, keyp2);
+}
+
+static const struct hashtab_key_params symtab_key_params = {
+	.hash = symhash,
+	.cmp = symcmp,
+};
+
+int symtab_init(struct symtab *s, u32 size)
+{
+	s->nprim = 0;
+	return hashtab_init(&s->table, size);
+}
+
+int symtab_insert(struct symtab *s, char *name, void *datum)
+{
+	return hashtab_insert(&s->table, name, datum, symtab_key_params);
+}
+
+void *symtab_search(const struct symtab *s, const char *name)
+{
+	return hashtab_search(&s->table, name, symtab_key_params);
+}