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, 73 insertions, 0 deletions

diff --git a/include/crypto/utils.h b/include/crypto/utils.h
new file mode 100644
index 000000000..2594f4577
--- /dev/null
+++ b/include/crypto/utils.h
@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Cryptographic utilities
+ *
+ * Copyright (c) 2023 Herbert Xu <herbert@gondor.apana.org.au>
+ */
+#ifndef _CRYPTO_UTILS_H
+#define _CRYPTO_UTILS_H
+
+#include <linux/unaligned.h>
+#include <linux/compiler_attributes.h>
+#include <linux/types.h>
+
+void __crypto_xor(u8 *dst, const u8 *src1, const u8 *src2, unsigned int size);
+
+static inline void crypto_xor(u8 *dst, const u8 *src, unsigned int size)
+{
+	if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) &&
+	    __builtin_constant_p(size) &&
+	    (size % sizeof(unsigned long)) == 0) {
+		unsigned long *d = (unsigned long *)dst;
+		unsigned long *s = (unsigned long *)src;
+		unsigned long l;
+
+		while (size > 0) {
+			l = get_unaligned(d) ^ get_unaligned(s++);
+			put_unaligned(l, d++);
+			size -= sizeof(unsigned long);
+		}
+	} else {
+		__crypto_xor(dst, dst, src, size);
+	}
+}
+
+static inline void crypto_xor_cpy(u8 *dst, const u8 *src1, const u8 *src2,
+				  unsigned int size)
+{
+	if (IS_ENABLED(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS) &&
+	    __builtin_constant_p(size) &&
+	    (size % sizeof(unsigned long)) == 0) {
+		unsigned long *d = (unsigned long *)dst;
+		unsigned long *s1 = (unsigned long *)src1;
+		unsigned long *s2 = (unsigned long *)src2;
+		unsigned long l;
+
+		while (size > 0) {
+			l = get_unaligned(s1++) ^ get_unaligned(s2++);
+			put_unaligned(l, d++);
+			size -= sizeof(unsigned long);
+		}
+	} else {
+		__crypto_xor(dst, src1, src2, size);
+	}
+}
+
+noinline unsigned long __crypto_memneq(const void *a, const void *b, size_t size);
+
+/**
+ * crypto_memneq - Compare two areas of memory without leaking
+ *		   timing information.
+ *
+ * @a: One area of memory
+ * @b: Another area of memory
+ * @size: The size of the area.
+ *
+ * Returns 0 when data is equal, 1 otherwise.
+ */
+static inline int crypto_memneq(const void *a, const void *b, size_t size)
+{
+	return __crypto_memneq(a, b, size) != 0UL ? 1 : 0;
+}
+
+#endif	/* _CRYPTO_UTILS_H */