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()

mm/kasan/kasan_test_c.c

@@ -1567,6 +1567,7 @@ static void kasan_memcmp(struct kunit *test)
 static void kasan_strings(struct kunit *test)
 {
 	char *ptr;
+	char *src;
 	size_t size = 24;
 
 	/*
@@ -1578,6 +1579,25 @@ static void kasan_strings(struct kunit *test)
 	ptr = kmalloc(size, GFP_KERNEL | __GFP_ZERO);
 	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ptr);
 
+	src = kmalloc(KASAN_GRANULE_SIZE, GFP_KERNEL | __GFP_ZERO);
+	strscpy(src, "f0cacc1a0000000", KASAN_GRANULE_SIZE);
+
+	/*
+	 * Make sure that strscpy() does not trigger KASAN if it overreads into
+	 * poisoned memory.
+	 *
+	 * The expected size does not include the terminator '\0'
+	 * so it is (KASAN_GRANULE_SIZE - 2) ==
+	 * KASAN_GRANULE_SIZE - ("initial removed character" + "\0").
+	 */
+	KUNIT_EXPECT_EQ(test, KASAN_GRANULE_SIZE - 2,
+			strscpy(ptr, src + 1, KASAN_GRANULE_SIZE));
+
+	/* strscpy should fail if the first byte is unreadable. */
+	KUNIT_EXPECT_KASAN_FAIL(test, strscpy(ptr, src + KASAN_GRANULE_SIZE,
+					      KASAN_GRANULE_SIZE));
+
+	kfree(src);
 	kfree(ptr);
 
 	/*