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/lib/crypto/nh.c b/lib/crypto/nh.c
new file mode 100644
index 000000000..e1d0095b5
--- /dev/null
+++ b/lib/crypto/nh.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2018 Google LLC
+ */
+
+/*
+ * Implementation of the NH almost-universal hash function, specifically the
+ * variant of NH used in Adiantum.  This is *not* a cryptographic hash function.
+ *
+ * Reference: section 6.3 of "Adiantum: length-preserving encryption for
+ * entry-level processors" (https://eprint.iacr.org/2018/720.pdf).
+ */
+
+#include <crypto/nh.h>
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/unaligned.h>
+
+#ifdef CONFIG_CRYPTO_LIB_NH_ARCH
+#include "nh.h" /* $(SRCARCH)/nh.h */
+#else
+static bool nh_arch(const u32 *key, const u8 *message, size_t message_len,
+		    __le64 hash[NH_NUM_PASSES])
+{
+	return false;
+}
+#endif
+
+void nh(const u32 *key, const u8 *message, size_t message_len,
+	__le64 hash[NH_NUM_PASSES])
+{
+	u64 sums[4] = { 0, 0, 0, 0 };
+
+	if (nh_arch(key, message, message_len, hash))
+		return;
+
+	static_assert(NH_PAIR_STRIDE == 2);
+	static_assert(NH_NUM_PASSES == 4);
+
+	while (message_len) {
+		u32 m0 = get_unaligned_le32(message + 0);
+		u32 m1 = get_unaligned_le32(message + 4);
+		u32 m2 = get_unaligned_le32(message + 8);
+		u32 m3 = get_unaligned_le32(message + 12);
+
+		sums[0] += (u64)(u32)(m0 + key[0]) * (u32)(m2 + key[2]);
+		sums[1] += (u64)(u32)(m0 + key[4]) * (u32)(m2 + key[6]);
+		sums[2] += (u64)(u32)(m0 + key[8]) * (u32)(m2 + key[10]);
+		sums[3] += (u64)(u32)(m0 + key[12]) * (u32)(m2 + key[14]);
+		sums[0] += (u64)(u32)(m1 + key[1]) * (u32)(m3 + key[3]);
+		sums[1] += (u64)(u32)(m1 + key[5]) * (u32)(m3 + key[7]);
+		sums[2] += (u64)(u32)(m1 + key[9]) * (u32)(m3 + key[11]);
+		sums[3] += (u64)(u32)(m1 + key[13]) * (u32)(m3 + key[15]);
+		key += NH_MESSAGE_UNIT / sizeof(key[0]);
+		message += NH_MESSAGE_UNIT;
+		message_len -= NH_MESSAGE_UNIT;
+	}
+
+	hash[0] = cpu_to_le64(sums[0]);
+	hash[1] = cpu_to_le64(sums[1]);
+	hash[2] = cpu_to_le64(sums[2]);
+	hash[3] = cpu_to_le64(sums[3]);
+}
+EXPORT_SYMBOL_GPL(nh);
+
+#ifdef nh_mod_init_arch
+static int __init nh_mod_init(void)
+{
+	nh_mod_init_arch();
+	return 0;
+}
+subsys_initcall(nh_mod_init);
+
+static void __exit nh_mod_exit(void)
+{
+}
+module_exit(nh_mod_exit);
+#endif
+
+MODULE_DESCRIPTION("NH almost-universal hash function");
+MODULE_LICENSE("GPL");