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, 106 insertions, 0 deletions

diff --git a/crypto/xxhash_generic.c b/crypto/xxhash_generic.c
new file mode 100644
index 000000000..175bb7ae0
--- /dev/null
+++ b/crypto/xxhash_generic.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <crypto/internal/hash.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/xxhash.h>
+#include <linux/unaligned.h>
+
+#define XXHASH64_BLOCK_SIZE	32
+#define XXHASH64_DIGEST_SIZE	8
+
+struct xxhash64_tfm_ctx {
+	u64 seed;
+};
+
+struct xxhash64_desc_ctx {
+	struct xxh64_state xxhstate;
+};
+
+static int xxhash64_setkey(struct crypto_shash *tfm, const u8 *key,
+			 unsigned int keylen)
+{
+	struct xxhash64_tfm_ctx *tctx = crypto_shash_ctx(tfm);
+
+	if (keylen != sizeof(tctx->seed))
+		return -EINVAL;
+	tctx->seed = get_unaligned_le64(key);
+	return 0;
+}
+
+static int xxhash64_init(struct shash_desc *desc)
+{
+	struct xxhash64_tfm_ctx *tctx = crypto_shash_ctx(desc->tfm);
+	struct xxhash64_desc_ctx *dctx = shash_desc_ctx(desc);
+
+	xxh64_reset(&dctx->xxhstate, tctx->seed);
+
+	return 0;
+}
+
+static int xxhash64_update(struct shash_desc *desc, const u8 *data,
+			 unsigned int length)
+{
+	struct xxhash64_desc_ctx *dctx = shash_desc_ctx(desc);
+
+	xxh64_update(&dctx->xxhstate, data, length);
+
+	return 0;
+}
+
+static int xxhash64_final(struct shash_desc *desc, u8 *out)
+{
+	struct xxhash64_desc_ctx *dctx = shash_desc_ctx(desc);
+
+	put_unaligned_le64(xxh64_digest(&dctx->xxhstate), out);
+
+	return 0;
+}
+
+static int xxhash64_digest(struct shash_desc *desc, const u8 *data,
+			 unsigned int length, u8 *out)
+{
+	struct xxhash64_tfm_ctx *tctx = crypto_shash_ctx(desc->tfm);
+
+	put_unaligned_le64(xxh64(data, length, tctx->seed), out);
+
+	return 0;
+}
+
+static struct shash_alg alg = {
+	.digestsize	= XXHASH64_DIGEST_SIZE,
+	.setkey		= xxhash64_setkey,
+	.init		= xxhash64_init,
+	.update		= xxhash64_update,
+	.final		= xxhash64_final,
+	.digest		= xxhash64_digest,
+	.descsize	= sizeof(struct xxhash64_desc_ctx),
+	.base		= {
+		.cra_name	 = "xxhash64",
+		.cra_driver_name = "xxhash64-generic",
+		.cra_priority	 = 100,
+		.cra_flags	 = CRYPTO_ALG_OPTIONAL_KEY,
+		.cra_blocksize	 = XXHASH64_BLOCK_SIZE,
+		.cra_ctxsize	 = sizeof(struct xxhash64_tfm_ctx),
+		.cra_module	 = THIS_MODULE,
+	}
+};
+
+static int __init xxhash_mod_init(void)
+{
+	return crypto_register_shash(&alg);
+}
+
+static void __exit xxhash_mod_fini(void)
+{
+	crypto_unregister_shash(&alg);
+}
+
+module_init(xxhash_mod_init);
+module_exit(xxhash_mod_fini);
+
+MODULE_AUTHOR("Nikolay Borisov <nborisov@suse.com>");
+MODULE_DESCRIPTION("xxhash calculations wrapper for lib/xxhash.c");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_CRYPTO("xxhash64");
+MODULE_ALIAS_CRYPTO("xxhash64-generic");