wcsmbs: Ensure wcstr worst-case linear execution time (BZ 23865)

It uses the same two-way algorithm used on strstr, strcasestr, and
memmem.  Different than strstr, neither the "shift table" optimization
nor the self-adapting filtering check is used because it would result in
a too-large shift table (and it also simplifies the implementation bit).

Checked on x86_64-linux-gnu and aarch64-linux-gnu.
Reviewed-by: DJ Delorie <dj@redhat.com>

1 files changed, 172 insertions, 0 deletions

diff --git a/string/test-strstr.c b/string/test-strstr.c
index 86237555c0..1eebdbcb51 100644
--- a/string/test-strstr.c
+++ b/string/test-strstr.c
@@ -59,6 +59,9 @@
 # undef weak_alias
 # define weak_alias(a, b)
 # define WCSSTR c_wcsstr
+# define __wmemcmp wmemcmp
+# define __wcsnlen wcsnlen
+# define __wcslen wcslen
 # include "wcsstr.c"
 # define C_IMPL WCSSTR
 #endif
@@ -217,6 +220,31 @@ check2 (void)
     }
 }
 
+static void
+check3 (void)
+{
+  /* Check that a long periodic needle does not cause false positives.  */
+  {
+    const CHAR input[] = L("F_BD_CE_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD"
+                            "_C3_88_20_EF_BF_BD_EF_BF_BD_EF_BF_BD"
+                            "_C3_A7_20_EF_BF_BD");
+    const CHAR need[] = L("_EF_BF_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD");
+    FOR_EACH_IMPL (impl, 0)
+      check_result (impl, input, need, NULL);
+  }
+
+  {
+    const CHAR input[] = L("F_BD_CE_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD"
+			   "_C3_88_20_EF_BF_BD_EF_BF_BD_EF_BF_BD"
+			   "_C3_A7_20_EF_BF_BD_DA_B5_C2_A6_20"
+			   "_EF_BF_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD");
+    const CHAR need[] = L("_EF_BF_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD_EF_BF_BD");
+    FOR_EACH_IMPL (impl, 0)
+      check_result (impl, input, need, (CHAR *) input + 115);
+  }
+}
+
+
 #define N 1024
 
 static void
@@ -243,6 +271,148 @@ pr23637 (void)
     check_result (impl, h, n, exp_result);
 }
 
+static void
+pr23865 (void)
+{
+  /* Check that a very long haystack is handled quickly if the needle is
+     short and occurs near the beginning.  */
+  {
+    size_t m = 1000000;
+    const CHAR *needle =
+      L("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
+        "AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA");
+    CHAR *haystack = xmalloc ((m + 1) * sizeof (CHAR));
+    MEMSET (haystack, L('A'), m);
+    haystack[0] = L('B');
+    haystack[m] = L('\0');
+
+    FOR_EACH_IMPL (impl, 0)
+      check_result (impl, haystack, needle, haystack + 1);
+
+    free (haystack);
+  }
+
+  /* Check that a very long needle is discarded quickly if the haystack is
+     short.  */
+  {
+    size_t m = 1000000;
+    const CHAR *haystack =
+      L("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
+	"ABABABABABABABABABABABABABABABABABABABABABABABABABABABABABABABABABAB");
+    CHAR *needle = xmalloc ((m + 1) * sizeof (CHAR));
+    MEMSET (needle, L'A', m);
+    needle[m] = L('\0');
+
+    FOR_EACH_IMPL (impl, 0)
+      check_result (impl, haystack, needle, NULL);
+
+    free (needle);
+  }
+
+  /* Check that the asymptotic worst-case complexity is not quadratic.  */
+  {
+    size_t m = 1000000;
+    CHAR *haystack = xmalloc ((2 * m + 2) * sizeof (CHAR));
+    CHAR *needle = xmalloc ((m + 2) * sizeof (CHAR));
+
+    MEMSET (haystack, L('A'), 2 * m);
+    haystack[2 * m] = L('B');
+    haystack[2 * m + 1] = L('\0');
+
+    MEMSET (needle, L('A'), m);
+    needle[m] = L('B');
+    needle[m + 1] = L('\0');
+
+    FOR_EACH_IMPL (impl, 0)
+      check_result (impl, haystack, needle, haystack + m);
+
+    free (needle);
+    free (haystack);
+  }
+
+  {
+    /* Ensure that with a barely periodic "short" needle, STRSTR's
+       search does not mistakenly skip just past the match point.  */
+    const CHAR *haystack =
+      L("\n"
+       "with_build_libsubdir\n"
+       "with_local_prefix\n"
+       "with_gxx_include_dir\n"
+       "with_cpp_install_dir\n"
+       "enable_generated_files_in_srcdir\n"
+       "with_gnu_ld\n"
+       "with_ld\n"
+       "with_demangler_in_ld\n"
+       "with_gnu_as\n"
+       "with_as\n"
+       "enable_largefile\n"
+       "enable_werror_always\n"
+       "enable_checking\n"
+       "enable_coverage\n"
+       "enable_gather_detailed_mem_stats\n"
+       "enable_build_with_cxx\n"
+       "with_stabs\n"
+       "enable_multilib\n"
+       "enable___cxa_atexit\n"
+       "enable_decimal_float\n"
+       "enable_fixed_point\n"
+       "enable_threads\n"
+       "enable_tls\n"
+       "enable_objc_gc\n"
+       "with_dwarf2\n"
+       "enable_shared\n"
+       "with_build_sysroot\n"
+       "with_sysroot\n"
+       "with_specs\n"
+       "with_pkgversion\n"
+       "with_bugurl\n"
+       "enable_languages\n"
+       "with_multilib_list\n");
+    const CHAR *needle =
+      L("\n"
+       "with_gnu_ld\n");
+
+    FOR_EACH_IMPL (impl, 0)
+      check_result (impl, haystack, needle, (CHAR*) haystack + 114);
+  }
+
+  {
+    /* Same bug, shorter trigger.  */
+    const CHAR *haystack = L("..wi.d.");
+    const CHAR *needle = L(".d.");
+    FOR_EACH_IMPL (impl, 0)
+      check_result (impl, haystack, needle, (CHAR*) haystack + 4);
+  }
+
+  /* Test case from Yves Bastide.
+     <https://www.openwall.com/lists/musl/2014/04/18/2>  */
+  {
+    const CHAR *input = L("playing play play play always");
+    const CHAR *needle = L("play play play");
+    FOR_EACH_IMPL (impl, 0)
+      check_result (impl, input, needle, (CHAR*) input + 8);
+  }
+
+  /* Test long needles.  */
+  {
+    size_t m = 1024;
+    CHAR *haystack = xmalloc ((2 * m + 1) * sizeof (CHAR));
+    CHAR *needle = xmalloc ((m + 1) * sizeof (CHAR));
+    haystack[0] = L('x');
+    MEMSET (haystack + 1, L(' '), m - 1);
+    MEMSET (haystack + m, L('x'), m);
+    haystack[2 * m] = L('\0');
+    MEMSET (needle, L('x'), m);
+    needle[m] = L('\0');
+
+    FOR_EACH_IMPL (impl, 0)
+      check_result (impl, haystack, needle, haystack + m);
+
+    free (needle);
+    free (haystack);
+  }
+}
+
 static int
 test_main (void)
 {
@@ -250,7 +420,9 @@ test_main (void)
 
   check1 ();
   check2 ();
+  check3 ();
   pr23637 ();
+  pr23865 ();
 
   printf ("%23s", "");
   FOR_EACH_IMPL (impl, 0)