x86-64 memchr/wmemchr: 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 memchr/wmemchr 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/memchr.S: Use RDX_LP for length.  Clear the
	upper 32 bits of RDX register.
	* sysdeps/x86_64/x32/Makefile (tests): Add tst-size_t-memchr.
	* sysdeps/x86_64/x32/test-size_t.h: New file.
	* sysdeps/x86_64/x32/tst-size_t-memchr.c: Likewise.

(cherry picked from commit 97700a34f36721b11a754cf37a1cc40695ece1fd)

6 files changed, 133 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index 399d162f03..c376a89cdc 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,13 @@
+2019-02-01  H.J. Lu  <hongjiu.lu@intel.com>
+
+	[BZ #24097]
+	CVE-2019-6488
+	* sysdeps/x86_64/memchr.S: Use RDX_LP for length.  Clear the
+	upper 32 bits of RDX register.
+	* sysdeps/x86_64/x32/Makefile (tests): Add tst-size_t-memchr.
+	* sysdeps/x86_64/x32/test-size_t.h: New file.
+	* sysdeps/x86_64/x32/tst-size_t-memchr.c: Likewise.
+
 2018-12-31  Florian Weimer  <fw@deneb.enyo.de>
 
 	[BZ #24027]
diff --git a/NEWS b/NEWS
index f7536ac0d9..dcf8ba65e7 100644
--- a/NEWS
+++ b/NEWS
@@ -60,6 +60,12 @@ Security related changes:
   architecture could write beyond the target buffer, resulting in a buffer
   overflow.  Reported by Andreas Schwab.
 
+  CVE-2019-6488: On x32, the size_t parameter may be passed in the lower
+  32 bits of a 64-bit register with with non-zero upper 32 bit.  When it
+  happened, accessing the 32-bit size_t value as the full 64-bit register
+  in the assembly string/memory functions would cause a buffer overflow.
+  Reported by H.J. Lu.
+
 The following bugs are resolved with this release:
 
   [20116] nptl: use after free in pthread_create
@@ -82,6 +88,7 @@ The following bugs are resolved with this release:
   [23196] string: __mempcpy_avx512_no_vzeroupper mishandles large copies
     (CVE-2018-11237)
   [24027] malloc: Integer overflow in realloc
+  [24097] Can't use 64-bit register for size_t in assembly codes for x32 (CVE-2019-6488)
 
 Version 2.24
 
diff --git a/sysdeps/x86_64/memchr.S b/sysdeps/x86_64/memchr.S
index 132eacba8f..b8c30a6fe4 100644
--- a/sysdeps/x86_64/memchr.S
+++ b/sysdeps/x86_64/memchr.S
@@ -24,9 +24,12 @@
 ENTRY(memchr)
 	movd	%rsi, %xmm1
 	mov	%rdi, %rcx
-
+#ifdef __ILP32__
+	/* Clear the upper 32 bits.  */
+	movl	%edx, %edx
+#endif
 	punpcklbw %xmm1, %xmm1
-	test	%rdx, %rdx
+	test	%RDX_LP, %RDX_LP
 	jz	L(return_null)
 	punpcklbw %xmm1, %xmm1
 
diff --git a/sysdeps/x86_64/x32/Makefile b/sysdeps/x86_64/x32/Makefile
index f2ebc24fb0..979273b3a8 100644
--- a/sysdeps/x86_64/x32/Makefile
+++ b/sysdeps/x86_64/x32/Makefile
@@ -4,3 +4,7 @@ ifeq ($(subdir),math)
 # 64-bit llround.  Add -fno-builtin-lround to silence the compiler.
 CFLAGS-s_llround.c += -fno-builtin-lround
 endif
+
+ifeq ($(subdir),string)
+tests += tst-size_t-memchr
+endif
diff --git a/sysdeps/x86_64/x32/test-size_t.h b/sysdeps/x86_64/x32/test-size_t.h
new file mode 100644
index 0000000000..78a940863e
--- /dev/null
+++ b/sysdeps/x86_64/x32/test-size_t.h
@@ -0,0 +1,35 @@
+/* Test string/memory functions 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/>.  */
+
+#define TEST_MAIN
+#include <string/test-string.h>
+
+/* On x32, parameter_t may be passed in a 64-bit register with the LEN
+   field in the lower 32 bits.  When the LEN field of 64-bit register
+   is passed to string/memory function as the size_t parameter, only
+   the lower 32 bits can be used.  */
+typedef struct
+{
+  union
+    {
+      size_t len;
+      void (*fn) (void);
+    };
+  void *p;
+} parameter_t;
diff --git a/sysdeps/x86_64/x32/tst-size_t-memchr.c b/sysdeps/x86_64/x32/tst-size_t-memchr.c
new file mode 100644
index 0000000000..ac77b86c08
--- /dev/null
+++ b/sysdeps/x86_64/x32/tst-size_t-memchr.c
@@ -0,0 +1,72 @@
+/* Test memchr 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/>.  */
+
+#ifndef WIDE
+# define TEST_NAME "memchr"
+#else
+# define TEST_NAME "wmemchr"
+#endif /* WIDE */
+#include "test-size_t.h"
+
+#ifndef WIDE
+# define MEMCHR memchr
+# define CHAR char
+# define UCHAR unsigned char
+#else
+# include <wchar.h>
+# define MEMCHR wmemchr
+# define CHAR wchar_t
+# define UCHAR wchar_t
+#endif /* WIDE */
+
+IMPL (MEMCHR, 1)
+
+typedef CHAR * (*proto_t) (const CHAR*, int, size_t);
+
+static CHAR *
+__attribute__ ((noinline, noclone))
+do_memchr (parameter_t a, parameter_t b)
+{
+  return CALL (&b, a.p, (uintptr_t) b.p, a.len);
+}
+
+static int
+test_main (void)
+{
+  test_init ();
+
+  parameter_t src = { { page_size / sizeof (CHAR) }, buf2 };
+  parameter_t c = { { 0 }, (void *) (uintptr_t) 0x12 };
+
+  int ret = 0;
+  FOR_EACH_IMPL (impl, 0)
+    {
+      c.fn = impl->fn;
+      CHAR *res = do_memchr (src, c);
+      if (res)
+	{
+	  error (0, 0, "Wrong result in function %s: %p != NULL",
+		 impl->name, res);
+	  ret = 1;
+	}
+    }
+
+  return ret ? EXIT_FAILURE : EXIT_SUCCESS;
+}
+
+#include <test-skeleton.c>