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, 78 insertions, 0 deletions

diff --git a/lib/crypto/curve25519.c b/lib/crypto/curve25519.c
new file mode 100644
index 000000000..01e265dfb
--- /dev/null
+++ b/lib/crypto/curve25519.c
@@ -0,0 +1,78 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+/*
+ * Copyright (C) 2015-2019 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ *
+ * This is an implementation of the Curve25519 ECDH algorithm, using either an
+ * architecture-optimized implementation or a generic implementation. The
+ * generic implementation is either 32-bit, or 64-bit with 128-bit integers,
+ * depending on what is supported by the target compiler.
+ *
+ * Information: https://cr.yp.to/ecdh.html
+ */
+
+#include <crypto/curve25519.h>
+#include <crypto/utils.h>
+#include <linux/export.h>
+#include <linux/init.h>
+#include <linux/module.h>
+
+static const u8 curve25519_null_point[CURVE25519_KEY_SIZE] __aligned(32) = { 0 };
+static const u8 curve25519_base_point[CURVE25519_KEY_SIZE] __aligned(32) = { 9 };
+
+#ifdef CONFIG_CRYPTO_LIB_CURVE25519_ARCH
+#include "curve25519.h" /* $(SRCARCH)/curve25519.h */
+#else
+static void curve25519_arch(u8 mypublic[CURVE25519_KEY_SIZE],
+			    const u8 secret[CURVE25519_KEY_SIZE],
+			    const u8 basepoint[CURVE25519_KEY_SIZE])
+{
+	curve25519_generic(mypublic, secret, basepoint);
+}
+
+static void curve25519_base_arch(u8 pub[CURVE25519_KEY_SIZE],
+				 const u8 secret[CURVE25519_KEY_SIZE])
+{
+	curve25519_generic(pub, secret, curve25519_base_point);
+}
+#endif
+
+bool __must_check
+curve25519(u8 mypublic[CURVE25519_KEY_SIZE],
+	   const u8 secret[CURVE25519_KEY_SIZE],
+	   const u8 basepoint[CURVE25519_KEY_SIZE])
+{
+	curve25519_arch(mypublic, secret, basepoint);
+	return crypto_memneq(mypublic, curve25519_null_point,
+			     CURVE25519_KEY_SIZE);
+}
+EXPORT_SYMBOL(curve25519);
+
+bool __must_check
+curve25519_generate_public(u8 pub[CURVE25519_KEY_SIZE],
+			   const u8 secret[CURVE25519_KEY_SIZE])
+{
+	if (unlikely(!crypto_memneq(secret, curve25519_null_point,
+				    CURVE25519_KEY_SIZE)))
+		return false;
+	curve25519_base_arch(pub, secret);
+	return crypto_memneq(pub, curve25519_null_point, CURVE25519_KEY_SIZE);
+}
+EXPORT_SYMBOL(curve25519_generate_public);
+
+#ifdef curve25519_mod_init_arch
+static int __init curve25519_mod_init(void)
+{
+	curve25519_mod_init_arch();
+	return 0;
+}
+subsys_initcall(curve25519_mod_init);
+
+static void __exit curve25519_mod_exit(void)
+{
+}
+module_exit(curve25519_mod_exit);
+#endif
+
+MODULE_LICENSE("GPL v2");
+MODULE_DESCRIPTION("Curve25519 algorithm");
+MODULE_AUTHOR("Jason A. Donenfeld <Jason@zx2c4.com>");