Merge tag 'hardening-v6.15-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull hardening fixes from Kees Cook:

 - lib/prime_numbers: KUnit test should not select PRIME_NUMBERS (Geert
   Uytterhoeven)

 - ubsan: Fix panic from test_ubsan_out_of_bounds (Mostafa Saleh)

 - ubsan: Remove 'default UBSAN' from UBSAN_INTEGER_WRAP (Nathan
   Chancellor)

 - string: Add load_unaligned_zeropad() code path to sized_strscpy()
   (Peter Collingbourne)

 - kasan: Add strscpy() test to trigger tag fault on arm64 (Vincenzo
   Frascino)

 - Disable GCC randstruct for COMPILE_TEST

* tag 'hardening-v6.15-rc3' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  lib/prime_numbers: KUnit test should not select PRIME_NUMBERS
  ubsan: Fix panic from test_ubsan_out_of_bounds
  lib/Kconfig.ubsan: Remove 'default UBSAN' from UBSAN_INTEGER_WRAP
  hardening: Disable GCC randstruct for COMPILE_TEST
  kasan: Add strscpy() test to trigger tag fault on arm64
  string: Add load_unaligned_zeropad() code path to sized_strscpy()

4 files changed, 22 insertions, 12 deletions

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 9fe4d8dfe578..f9051ab610d5 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -3290,7 +3290,7 @@ config GCD_KUNIT_TEST
 config PRIME_NUMBERS_KUNIT_TEST
 	tristate "Prime number generator test" if !KUNIT_ALL_TESTS
 	depends on KUNIT
-	select PRIME_NUMBERS
+	depends on PRIME_NUMBERS
 	default KUNIT_ALL_TESTS
 	help
 	  This option enables the KUnit test suite for the {is,next}_prime_number
diff --git a/lib/Kconfig.ubsan b/lib/Kconfig.ubsan
index 4216b3a4ff21..f6ea0c5b5da3 100644
--- a/lib/Kconfig.ubsan
+++ b/lib/Kconfig.ubsan
@@ -118,7 +118,6 @@ config UBSAN_UNREACHABLE
 
 config UBSAN_INTEGER_WRAP
 	bool "Perform checking for integer arithmetic wrap-around"
-	default UBSAN
 	depends on !COMPILE_TEST
 	depends on $(cc-option,-fsanitize-undefined-ignore-overflow-pattern=all)
 	depends on $(cc-option,-fsanitize=signed-integer-overflow)
diff --git a/lib/string.c b/lib/string.c
index eb4486ed40d2..b632c71df1a5 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -119,6 +119,7 @@ ssize_t sized_strscpy(char *dest, const char *src, size_t count)
 	if (count == 0 || WARN_ON_ONCE(count > INT_MAX))
 		return -E2BIG;
 
+#ifndef CONFIG_DCACHE_WORD_ACCESS
 #ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
 	/*
 	 * If src is unaligned, don't cross a page boundary,
@@ -134,11 +135,13 @@ ssize_t sized_strscpy(char *dest, const char *src, size_t count)
 	if (((long) dest | (long) src) & (sizeof(long) - 1))
 		max = 0;
 #endif
+#endif
 
 	/*
-	 * read_word_at_a_time() below may read uninitialized bytes after the
-	 * trailing zero and use them in comparisons. Disable this optimization
-	 * under KMSAN to prevent false positive reports.
+	 * load_unaligned_zeropad() or read_word_at_a_time() below may read
+	 * uninitialized bytes after the trailing zero and use them in
+	 * comparisons. Disable this optimization under KMSAN to prevent
+	 * false positive reports.
 	 */
 	if (IS_ENABLED(CONFIG_KMSAN))
 		max = 0;
@@ -146,7 +149,11 @@ ssize_t sized_strscpy(char *dest, const char *src, size_t count)
 	while (max >= sizeof(unsigned long)) {
 		unsigned long c, data;
 
+#ifdef CONFIG_DCACHE_WORD_ACCESS
+		c = load_unaligned_zeropad(src+res);
+#else
 		c = read_word_at_a_time(src+res);
+#endif
 		if (has_zero(c, &data, &constants)) {
 			data = prep_zero_mask(c, data, &constants);
 			data = create_zero_mask(data);
diff --git a/lib/test_ubsan.c b/lib/test_ubsan.c
index 8772e5edaa4f..a4b6f52b9c57 100644
--- a/lib/test_ubsan.c
+++ b/lib/test_ubsan.c
@@ -77,18 +77,22 @@ static void test_ubsan_shift_out_of_bounds(void)
 
 static void test_ubsan_out_of_bounds(void)
 {
-	volatile int i = 4, j = 5, k = -1;
-	volatile char above[4] = { }; /* Protect surrounding memory. */
-	volatile int arr[4];
-	volatile char below[4] = { }; /* Protect surrounding memory. */
+	int i = 4, j = 4, k = -1;
+	volatile struct {
+		char above[4]; /* Protect surrounding memory. */
+		int arr[4];
+		char below[4]; /* Protect surrounding memory. */
+	} data;
 
-	above[0] = below[0];
+	OPTIMIZER_HIDE_VAR(i);
+	OPTIMIZER_HIDE_VAR(j);
+	OPTIMIZER_HIDE_VAR(k);
 
 	UBSAN_TEST(CONFIG_UBSAN_BOUNDS, "above");
-	arr[j] = i;
+	data.arr[j] = i;
 
 	UBSAN_TEST(CONFIG_UBSAN_BOUNDS, "below");
-	arr[k] = i;
+	data.arr[k] = i;
 }
 
 enum ubsan_test_enum {