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, 116 insertions, 0 deletions

diff --git a/fs/ntfs3/upcase.c b/fs/ntfs3/upcase.c
new file mode 100644
index 000000000..7681eefac
--- /dev/null
+++ b/fs/ntfs3/upcase.c
@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ *
+ * Copyright (C) 2019-2021 Paragon Software GmbH, All rights reserved.
+ *
+ */
+
+#include <linux/kernel.h>
+#include <linux/types.h>
+
+#include "ntfs_fs.h"
+
+static inline u16 upcase_unicode_char(const u16 *upcase, u16 chr)
+{
+	if (chr < 'a')
+		return chr;
+
+	if (chr <= 'z')
+		return chr - ('a' - 'A');
+
+	return upcase[chr];
+}
+
+/*
+ * ntfs_cmp_names
+ *
+ * Thanks Kari Argillander <kari.argillander@gmail.com> for idea and implementation 'bothcase'
+ *
+ * Straight way to compare names:
+ * - Case insensitive
+ * - If name equals and 'bothcases' then
+ * - Case sensitive
+ * 'Straight way' code scans input names twice in worst case.
+ * Optimized code scans input names only once.
+ */
+int ntfs_cmp_names(const __le16 *s1, size_t l1, const __le16 *s2, size_t l2,
+		   const u16 *upcase, bool bothcase)
+{
+	int diff1 = 0;
+	int diff2;
+	size_t len = min(l1, l2);
+
+	if (!bothcase && upcase)
+		goto case_insentive;
+
+	for (; len; s1++, s2++, len--) {
+		diff1 = le16_to_cpu(*s1) - le16_to_cpu(*s2);
+		if (diff1) {
+			if (bothcase && upcase)
+				goto case_insentive;
+
+			return diff1;
+		}
+	}
+	return l1 - l2;
+
+case_insentive:
+	for (; len; s1++, s2++, len--) {
+		diff2 = upcase_unicode_char(upcase, le16_to_cpu(*s1)) -
+			upcase_unicode_char(upcase, le16_to_cpu(*s2));
+		if (diff2)
+			return diff2;
+	}
+
+	diff2 = l1 - l2;
+	return diff2 ? diff2 : diff1;
+}
+
+int ntfs_cmp_names_cpu(const struct cpu_str *uni1, const struct le_str *uni2,
+		       const u16 *upcase, bool bothcase)
+{
+	const u16 *s1 = uni1->name;
+	const __le16 *s2 = uni2->name;
+	size_t l1 = uni1->len;
+	size_t l2 = uni2->len;
+	size_t len = min(l1, l2);
+	int diff1 = 0;
+	int diff2;
+
+	if (!bothcase && upcase)
+		goto case_insentive;
+
+	for (; len; s1++, s2++, len--) {
+		diff1 = *s1 - le16_to_cpu(*s2);
+		if (diff1) {
+			if (bothcase && upcase)
+				goto case_insentive;
+
+			return diff1;
+		}
+	}
+	return l1 - l2;
+
+case_insentive:
+	for (; len; s1++, s2++, len--) {
+		diff2 = upcase_unicode_char(upcase, *s1) -
+			upcase_unicode_char(upcase, le16_to_cpu(*s2));
+		if (diff2)
+			return diff2;
+	}
+
+	diff2 = l1 - l2;
+	return diff2 ? diff2 : diff1;
+}
+
+/* Helper function for ntfs_d_hash. */
+unsigned long ntfs_names_hash(const u16 *name, size_t len, const u16 *upcase,
+			      unsigned long hash)
+{
+	while (len--) {
+		unsigned int c = upcase_unicode_char(upcase, *name++);
+		hash = partial_name_hash(c, hash);
+	}
+
+	return hash;
+}