String: Add overflow tests for strnlen, memchr, and strncat [BZ #27974]

This commit adds tests for a bug in the wide char variant of the
functions where the implementation may assume that maxlen for wcsnlen
or n for wmemchr/strncat will not overflow when multiplied by
sizeof(wchar_t).

These tests show the following implementations failing on x86_64:

wcsnlen-sse4_1
wcsnlen-avx2

wmemchr-sse2
wmemchr-avx2

strncat would fail as well if it where on a system that prefered
either of the wcsnlen implementations that failed as it relies on
wcsnlen.

Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/string/test-strnlen.c b/string/test-strnlen.c
index 920f58e97b..f53e09263f 100644
--- a/string/test-strnlen.c
+++ b/string/test-strnlen.c
@@ -90,6 +90,38 @@ do_test (size_t align, size_t len, size_t maxlen, int max_char)
 }
 
 static void
+do_overflow_tests (void)
+{
+  size_t i, j, len;
+  const size_t one = 1;
+  uintptr_t buf_addr = (uintptr_t) buf1;
+
+  for (i = 0; i < 750; ++i)
+    {
+      do_test (0, i, SIZE_MAX - i, BIG_CHAR);
+      do_test (0, i, i - buf_addr, BIG_CHAR);
+      do_test (0, i, -buf_addr - i, BIG_CHAR);
+      do_test (0, i, SIZE_MAX - buf_addr - i, BIG_CHAR);
+      do_test (0, i, SIZE_MAX - buf_addr + i, BIG_CHAR);
+
+      len = 0;
+      for (j = 8 * sizeof(size_t) - 1; j ; --j)
+        {
+          len |= one << j;
+          do_test (0, i, len - i, BIG_CHAR);
+          do_test (0, i, len + i, BIG_CHAR);
+          do_test (0, i, len - buf_addr - i, BIG_CHAR);
+          do_test (0, i, len - buf_addr + i, BIG_CHAR);
+
+          do_test (0, i, ~len - i, BIG_CHAR);
+          do_test (0, i, ~len + i, BIG_CHAR);
+          do_test (0, i, ~len - buf_addr - i, BIG_CHAR);
+          do_test (0, i, ~len - buf_addr + i, BIG_CHAR);
+        }
+    }
+}
+
+static void
 do_random_tests (void)
 {
   size_t i, j, n, align, len;
@@ -283,6 +315,7 @@ test_main (void)
   do_random_tests ();
   do_page_tests ();
   do_page_2_tests ();
+  do_overflow_tests ();
   return ret;
 }