x86-64 strnlen/wcsnlen: Properly handle the length parameter [BZ #24097]

On x32, the size_t parameter may be passed in the lower 32 bits of a
64-bit register with the non-zero upper 32 bits.  The string/memory
functions written in assembly can only use the lower 32 bits of a
64-bit register as length or must clear the upper 32 bits before using
the full 64-bit register for length.

This pach fixes strnlen/wcsnlen for x32.  Tested on x86-64 and x32.  On
x86-64, libc.so is the same with and withou the fix.

	[BZ #24097]
	CVE-2019-6488
	* sysdeps/x86_64/strlen.S: Use RSI_LP for length.
	* sysdeps/x86_64/x32/Makefile (tests): Add tst-size_t-strnlen.
	* sysdeps/x86_64/x32/tst-size_t-strnlen.c: New file.

(cherry picked from commit 5165de69c0908e28a380cbd4bb054e55ea4abc95)

2 files changed, 73 insertions, 1 deletions

diff --git a/sysdeps/x86_64/x32/Makefile b/sysdeps/x86_64/x32/Makefile
index ae0606c703..35d41d9bae 100644
--- a/sysdeps/x86_64/x32/Makefile
+++ b/sysdeps/x86_64/x32/Makefile
@@ -8,7 +8,7 @@ endif
 ifeq ($(subdir),string)
 tests += tst-size_t-memchr tst-size_t-memcmp tst-size_t-memcpy \
 	 tst-size_t-memrchr tst-size_t-memset tst-size_t-strncasecmp \
-	 tst-size_t-strncmp tst-size_t-strncpy
+	 tst-size_t-strncmp tst-size_t-strncpy tst-size_t-strnlen
 endif
 
 ifeq ($(subdir),wcsmbs)
diff --git a/sysdeps/x86_64/x32/tst-size_t-strnlen.c b/sysdeps/x86_64/x32/tst-size_t-strnlen.c
new file mode 100644
index 0000000000..1f2f0b9e0f
--- /dev/null
+++ b/sysdeps/x86_64/x32/tst-size_t-strnlen.c
@@ -0,0 +1,72 @@
+/* Test strnlen with size_t in the lower 32 bits of 64-bit register.
+   Copyright (C) 2019 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <http://www.gnu.org/licenses/>.  */
+
+#ifdef WIDE
+# define TEST_NAME "wcsnlen"
+#else
+# define TEST_NAME "strnlen"
+#endif /* WIDE */
+
+#include "test-size_t.h"
+
+#ifdef WIDE
+# include <wchar.h>
+# define STRNLEN wcsnlen
+# define CHAR wchar_t
+#else
+# define STRNLEN strnlen
+# define CHAR char
+#endif /* WIDE */
+
+IMPL (STRNLEN, 1)
+
+typedef size_t (*proto_t) (const CHAR *, size_t);
+
+static size_t
+__attribute__ ((noinline, noclone))
+do_strnlen (parameter_t a, parameter_t b)
+{
+  return CALL (&a, a.p, b.len);
+}
+
+static int
+test_main (void)
+{
+  test_init ();
+
+  size_t size = page_size / sizeof (CHAR);
+  parameter_t src = { { 0 }, buf2 };
+  parameter_t c = { { size }, (void *) (uintptr_t) 'a' };
+
+  int ret = 0;
+  FOR_EACH_IMPL (impl, 0)
+    {
+      src.fn = impl->fn;
+      size_t res = do_strnlen (src, c);
+      if (res != size)
+	{
+	  error (0, 0, "Wrong result in function %s: 0x%x != 0x%x",
+		 impl->name, res, size);
+	  ret = 1;
+	}
+    }
+
+  return ret ? EXIT_FAILURE : EXIT_SUCCESS;
+}
+
+#include <test-skeleton.c>