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, 191 insertions, 0 deletions

diff --git a/crypto/xctr.c b/crypto/xctr.c
new file mode 100644
index 000000000..607ab82cb
--- /dev/null
+++ b/crypto/xctr.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * XCTR: XOR Counter mode - Adapted from ctr.c
+ *
+ * (C) Copyright IBM Corp. 2007 - Joy Latten <latten@us.ibm.com>
+ * Copyright 2021 Google LLC
+ */
+
+/*
+ * XCTR mode is a blockcipher mode of operation used to implement HCTR2. XCTR is
+ * closely related to the CTR mode of operation; the main difference is that CTR
+ * generates the keystream using E(CTR + IV) whereas XCTR generates the
+ * keystream using E(CTR ^ IV). This allows implementations to avoid dealing
+ * with multi-limb integers (as is required in CTR mode). XCTR is also specified
+ * using little-endian arithmetic which makes it slightly faster on LE machines.
+ *
+ * See the HCTR2 paper for more details:
+ *	Length-preserving encryption with HCTR2
+ *      (https://eprint.iacr.org/2021/1441.pdf)
+ */
+
+#include <crypto/algapi.h>
+#include <crypto/internal/cipher.h>
+#include <crypto/internal/skcipher.h>
+#include <linux/err.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+
+/* For now this implementation is limited to 16-byte blocks for simplicity */
+#define XCTR_BLOCKSIZE 16
+
+static void crypto_xctr_crypt_final(struct skcipher_walk *walk,
+				   struct crypto_cipher *tfm, u32 byte_ctr)
+{
+	u8 keystream[XCTR_BLOCKSIZE];
+	const u8 *src = walk->src.virt.addr;
+	u8 *dst = walk->dst.virt.addr;
+	unsigned int nbytes = walk->nbytes;
+	__le32 ctr32 = cpu_to_le32(byte_ctr / XCTR_BLOCKSIZE + 1);
+
+	crypto_xor(walk->iv, (u8 *)&ctr32, sizeof(ctr32));
+	crypto_cipher_encrypt_one(tfm, keystream, walk->iv);
+	crypto_xor_cpy(dst, keystream, src, nbytes);
+	crypto_xor(walk->iv, (u8 *)&ctr32, sizeof(ctr32));
+}
+
+static int crypto_xctr_crypt_segment(struct skcipher_walk *walk,
+				    struct crypto_cipher *tfm, u32 byte_ctr)
+{
+	void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
+		   crypto_cipher_alg(tfm)->cia_encrypt;
+	const u8 *src = walk->src.virt.addr;
+	u8 *dst = walk->dst.virt.addr;
+	unsigned int nbytes = walk->nbytes;
+	__le32 ctr32 = cpu_to_le32(byte_ctr / XCTR_BLOCKSIZE + 1);
+
+	do {
+		crypto_xor(walk->iv, (u8 *)&ctr32, sizeof(ctr32));
+		fn(crypto_cipher_tfm(tfm), dst, walk->iv);
+		crypto_xor(dst, src, XCTR_BLOCKSIZE);
+		crypto_xor(walk->iv, (u8 *)&ctr32, sizeof(ctr32));
+
+		le32_add_cpu(&ctr32, 1);
+
+		src += XCTR_BLOCKSIZE;
+		dst += XCTR_BLOCKSIZE;
+	} while ((nbytes -= XCTR_BLOCKSIZE) >= XCTR_BLOCKSIZE);
+
+	return nbytes;
+}
+
+static int crypto_xctr_crypt_inplace(struct skcipher_walk *walk,
+				    struct crypto_cipher *tfm, u32 byte_ctr)
+{
+	void (*fn)(struct crypto_tfm *, u8 *, const u8 *) =
+		   crypto_cipher_alg(tfm)->cia_encrypt;
+	unsigned long alignmask = crypto_cipher_alignmask(tfm);
+	unsigned int nbytes = walk->nbytes;
+	u8 *data = walk->dst.virt.addr;
+	u8 tmp[XCTR_BLOCKSIZE + MAX_CIPHER_ALIGNMASK];
+	u8 *keystream = PTR_ALIGN(tmp + 0, alignmask + 1);
+	__le32 ctr32 = cpu_to_le32(byte_ctr / XCTR_BLOCKSIZE + 1);
+
+	do {
+		crypto_xor(walk->iv, (u8 *)&ctr32, sizeof(ctr32));
+		fn(crypto_cipher_tfm(tfm), keystream, walk->iv);
+		crypto_xor(data, keystream, XCTR_BLOCKSIZE);
+		crypto_xor(walk->iv, (u8 *)&ctr32, sizeof(ctr32));
+
+		le32_add_cpu(&ctr32, 1);
+
+		data += XCTR_BLOCKSIZE;
+	} while ((nbytes -= XCTR_BLOCKSIZE) >= XCTR_BLOCKSIZE);
+
+	return nbytes;
+}
+
+static int crypto_xctr_crypt(struct skcipher_request *req)
+{
+	struct crypto_skcipher *tfm = crypto_skcipher_reqtfm(req);
+	struct crypto_cipher *cipher = skcipher_cipher_simple(tfm);
+	struct skcipher_walk walk;
+	unsigned int nbytes;
+	int err;
+	u32 byte_ctr = 0;
+
+	err = skcipher_walk_virt(&walk, req, false);
+
+	while (walk.nbytes >= XCTR_BLOCKSIZE) {
+		if (walk.src.virt.addr == walk.dst.virt.addr)
+			nbytes = crypto_xctr_crypt_inplace(&walk, cipher,
+							   byte_ctr);
+		else
+			nbytes = crypto_xctr_crypt_segment(&walk, cipher,
+							   byte_ctr);
+
+		byte_ctr += walk.nbytes - nbytes;
+		err = skcipher_walk_done(&walk, nbytes);
+	}
+
+	if (walk.nbytes) {
+		crypto_xctr_crypt_final(&walk, cipher, byte_ctr);
+		err = skcipher_walk_done(&walk, 0);
+	}
+
+	return err;
+}
+
+static int crypto_xctr_create(struct crypto_template *tmpl, struct rtattr **tb)
+{
+	struct skcipher_instance *inst;
+	struct crypto_alg *alg;
+	int err;
+
+	inst = skcipher_alloc_instance_simple(tmpl, tb);
+	if (IS_ERR(inst))
+		return PTR_ERR(inst);
+
+	alg = skcipher_ialg_simple(inst);
+
+	/* Block size must be 16 bytes. */
+	err = -EINVAL;
+	if (alg->cra_blocksize != XCTR_BLOCKSIZE)
+		goto out_free_inst;
+
+	/* XCTR mode is a stream cipher. */
+	inst->alg.base.cra_blocksize = 1;
+
+	/*
+	 * To simplify the implementation, configure the skcipher walk to only
+	 * give a partial block at the very end, never earlier.
+	 */
+	inst->alg.chunksize = alg->cra_blocksize;
+
+	inst->alg.encrypt = crypto_xctr_crypt;
+	inst->alg.decrypt = crypto_xctr_crypt;
+
+	err = skcipher_register_instance(tmpl, inst);
+	if (err) {
+out_free_inst:
+		inst->free(inst);
+	}
+
+	return err;
+}
+
+static struct crypto_template crypto_xctr_tmpl = {
+	.name = "xctr",
+	.create = crypto_xctr_create,
+	.module = THIS_MODULE,
+};
+
+static int __init crypto_xctr_module_init(void)
+{
+	return crypto_register_template(&crypto_xctr_tmpl);
+}
+
+static void __exit crypto_xctr_module_exit(void)
+{
+	crypto_unregister_template(&crypto_xctr_tmpl);
+}
+
+module_init(crypto_xctr_module_init);
+module_exit(crypto_xctr_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("XCTR block cipher mode of operation");
+MODULE_ALIAS_CRYPTO("xctr");
+MODULE_IMPORT_NS("CRYPTO_INTERNAL");