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, 82 insertions, 0 deletions

diff --git a/crypto/arc4.c b/crypto/arc4.c
new file mode 100644
index 000000000..160801811
--- /dev/null
+++ b/crypto/arc4.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Cryptographic API
+ *
+ * ARC4 Cipher Algorithm
+ *
+ * Jon Oberheide <jon@oberheide.org>
+ */
+
+#include <crypto/arc4.h>
+#include <crypto/internal/skcipher.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/sched.h>
+
+#define ARC4_ALIGN __alignof__(struct arc4_ctx)
+
+static int crypto_arc4_setkey(struct crypto_lskcipher *tfm, const u8 *in_key,
+			      unsigned int key_len)
+{
+	struct arc4_ctx *ctx = crypto_lskcipher_ctx(tfm);
+
+	return arc4_setkey(ctx, in_key, key_len);
+}
+
+static int crypto_arc4_crypt(struct crypto_lskcipher *tfm, const u8 *src,
+			     u8 *dst, unsigned nbytes, u8 *siv, u32 flags)
+{
+	struct arc4_ctx *ctx = crypto_lskcipher_ctx(tfm);
+
+	if (!(flags & CRYPTO_LSKCIPHER_FLAG_CONT))
+		memcpy(siv, ctx, sizeof(*ctx));
+
+	ctx = (struct arc4_ctx *)siv;
+
+	arc4_crypt(ctx, dst, src, nbytes);
+	return 0;
+}
+
+static int crypto_arc4_init(struct crypto_lskcipher *tfm)
+{
+	pr_warn_ratelimited("\"%s\" (%ld) uses obsolete ecb(arc4) skcipher\n",
+			    current->comm, (unsigned long)current->pid);
+
+	return 0;
+}
+
+static struct lskcipher_alg arc4_alg = {
+	.co.base.cra_name		=	"arc4",
+	.co.base.cra_driver_name	=	"arc4-generic",
+	.co.base.cra_priority		=	100,
+	.co.base.cra_blocksize		=	ARC4_BLOCK_SIZE,
+	.co.base.cra_ctxsize		=	sizeof(struct arc4_ctx),
+	.co.base.cra_alignmask		=	ARC4_ALIGN - 1,
+	.co.base.cra_module		=	THIS_MODULE,
+	.co.min_keysize			=	ARC4_MIN_KEY_SIZE,
+	.co.max_keysize			=	ARC4_MAX_KEY_SIZE,
+	.co.statesize			=	sizeof(struct arc4_ctx),
+	.setkey				=	crypto_arc4_setkey,
+	.encrypt			=	crypto_arc4_crypt,
+	.decrypt			=	crypto_arc4_crypt,
+	.init				=	crypto_arc4_init,
+};
+
+static int __init arc4_init(void)
+{
+	return crypto_register_lskcipher(&arc4_alg);
+}
+
+static void __exit arc4_exit(void)
+{
+	crypto_unregister_lskcipher(&arc4_alg);
+}
+
+module_init(arc4_init);
+module_exit(arc4_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("ARC4 Cipher Algorithm");
+MODULE_AUTHOR("Jon Oberheide <jon@oberheide.org>");
+MODULE_ALIAS_CRYPTO("ecb(arc4)");