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, 133 insertions, 0 deletions

diff --git a/fs/hfs/string_test.c b/fs/hfs/string_test.c
new file mode 100644
index 000000000..e1bf6f954
--- /dev/null
+++ b/fs/hfs/string_test.c
@@ -0,0 +1,133 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * KUnit tests for HFS string operations
+ *
+ * Copyright (C) 2025 Viacheslav Dubeyko <slava@dubeyko.com>
+ */
+
+#include <kunit/test.h>
+#include <linux/dcache.h>
+#include "hfs_fs.h"
+
+/* Test hfs_strcmp function */
+static void hfs_strcmp_test(struct kunit *test)
+{
+	/* Test equal strings */
+	KUNIT_EXPECT_EQ(test, 0, hfs_strcmp("hello", 5, "hello", 5));
+	KUNIT_EXPECT_EQ(test, 0, hfs_strcmp("test", 4, "test", 4));
+	KUNIT_EXPECT_EQ(test, 0, hfs_strcmp("", 0, "", 0));
+
+	/* Test unequal strings */
+	KUNIT_EXPECT_NE(test, 0, hfs_strcmp("hello", 5, "world", 5));
+	KUNIT_EXPECT_NE(test, 0, hfs_strcmp("test", 4, "testing", 7));
+
+	/* Test different lengths */
+	KUNIT_EXPECT_LT(test, hfs_strcmp("test", 4, "testing", 7), 0);
+	KUNIT_EXPECT_GT(test, hfs_strcmp("testing", 7, "test", 4), 0);
+
+	/* Test case insensitive comparison (HFS should handle case) */
+	KUNIT_EXPECT_EQ(test, 0, hfs_strcmp("Test", 4, "TEST", 4));
+	KUNIT_EXPECT_EQ(test, 0, hfs_strcmp("hello", 5, "HELLO", 5));
+
+	/* Test with special characters */
+	KUNIT_EXPECT_EQ(test, 0, hfs_strcmp("file.txt", 8, "file.txt", 8));
+	KUNIT_EXPECT_NE(test, 0, hfs_strcmp("file.txt", 8, "file.dat", 8));
+
+	/* Test boundary cases */
+	KUNIT_EXPECT_EQ(test, 0, hfs_strcmp("a", 1, "a", 1));
+	KUNIT_EXPECT_NE(test, 0, hfs_strcmp("a", 1, "b", 1));
+}
+
+/* Test hfs_hash_dentry function */
+static void hfs_hash_dentry_test(struct kunit *test)
+{
+	struct qstr test_name1, test_name2, test_name3;
+	struct dentry dentry = {};
+	char name1[] = "testfile";
+	char name2[] = "TestFile";
+	char name3[] = "different";
+
+	/* Initialize test strings */
+	test_name1.name = name1;
+	test_name1.len = strlen(name1);
+	test_name1.hash = 0;
+
+	test_name2.name = name2;
+	test_name2.len = strlen(name2);
+	test_name2.hash = 0;
+
+	test_name3.name = name3;
+	test_name3.len = strlen(name3);
+	test_name3.hash = 0;
+
+	/* Test hashing */
+	KUNIT_EXPECT_EQ(test, 0, hfs_hash_dentry(&dentry, &test_name1));
+	KUNIT_EXPECT_EQ(test, 0, hfs_hash_dentry(&dentry, &test_name2));
+	KUNIT_EXPECT_EQ(test, 0, hfs_hash_dentry(&dentry, &test_name3));
+
+	/* Case insensitive names should hash the same */
+	KUNIT_EXPECT_EQ(test, test_name1.hash, test_name2.hash);
+
+	/* Different names should have different hashes */
+	KUNIT_EXPECT_NE(test, test_name1.hash, test_name3.hash);
+}
+
+/* Test hfs_compare_dentry function */
+static void hfs_compare_dentry_test(struct kunit *test)
+{
+	struct qstr test_name;
+	struct dentry dentry = {};
+	char name[] = "TestFile";
+
+	test_name.name = name;
+	test_name.len = strlen(name);
+
+	/* Test exact match */
+	KUNIT_EXPECT_EQ(test, 0, hfs_compare_dentry(&dentry, 8,
+						    "TestFile", &test_name));
+
+	/* Test case insensitive match */
+	KUNIT_EXPECT_EQ(test, 0, hfs_compare_dentry(&dentry, 8,
+						    "testfile", &test_name));
+	KUNIT_EXPECT_EQ(test, 0, hfs_compare_dentry(&dentry, 8,
+						    "TESTFILE", &test_name));
+
+	/* Test different names */
+	KUNIT_EXPECT_EQ(test, 1, hfs_compare_dentry(&dentry, 8,
+						    "DiffFile", &test_name));
+
+	/* Test different lengths */
+	KUNIT_EXPECT_EQ(test, 1, hfs_compare_dentry(&dentry, 7,
+						    "TestFil", &test_name));
+	KUNIT_EXPECT_EQ(test, 1, hfs_compare_dentry(&dentry, 9,
+						    "TestFiles", &test_name));
+
+	/* Test empty string */
+	test_name.name = "";
+	test_name.len = 0;
+	KUNIT_EXPECT_EQ(test, 0, hfs_compare_dentry(&dentry, 0, "", &test_name));
+
+	/* Test HFS_NAMELEN boundary */
+	test_name.name = "This_is_a_very_long_filename_that_exceeds_normal_limits";
+	test_name.len = strlen(test_name.name);
+	KUNIT_EXPECT_EQ(test, 0, hfs_compare_dentry(&dentry, HFS_NAMELEN,
+			"This_is_a_very_long_filename_th", &test_name));
+}
+
+static struct kunit_case hfs_string_test_cases[] = {
+	KUNIT_CASE(hfs_strcmp_test),
+	KUNIT_CASE(hfs_hash_dentry_test),
+	KUNIT_CASE(hfs_compare_dentry_test),
+	{}
+};
+
+static struct kunit_suite hfs_string_test_suite = {
+	.name = "hfs_string",
+	.test_cases = hfs_string_test_cases,
+};
+
+kunit_test_suite(hfs_string_test_suite);
+
+MODULE_DESCRIPTION("KUnit tests for HFS string operations");
+MODULE_LICENSE("GPL");
+MODULE_IMPORT_NS("EXPORTED_FOR_KUNIT_TESTING");