From a107bd201f836b1d82e1a9086a2a48625ac1c0dd Mon Sep 17 00:00:00 2001

From: "H.J. Lu" <hjl.tools@gmail.com>

Date: Wed, 2 Mar 2022 13:52:42 -0800

Subject: [PATCH] x86-64 memcmp/wmemcmp: 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 memcmp/wmemcmp 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/multiarch/memcmp-avx2-movbe.S: Use RDX_LP for

	length.  Clear the upper 32 bits of RDX register.

	* sysdeps/x86_64/multiarch/memcmp-sse4.S: Likewise.

	* sysdeps/x86_64/multiarch/memcmp-ssse3.S: Likewise.

	* sysdeps/x86_64/x32/Makefile (tests): Add tst-size_t-memcmp and

	tst-size_t-wmemcmp.

	* sysdeps/x86_64/x32/tst-size_t-memcmp.c: New file.

	* sysdeps/x86_64/x32/tst-size_t-wmemcmp.c: Likewise.

(cherry picked from commit b304fc201d2f6baf52ea790df8643e99772243cd)

---

 sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S |  7 +-

 sysdeps/x86_64/multiarch/memcmp-sse4.S       |  9 ++-

 sysdeps/x86_64/multiarch/memcmp-ssse3.S      |  7 +-

 sysdeps/x86_64/x32/Makefile                  |  4 +-

 sysdeps/x86_64/x32/tst-size_t-memcmp.c       | 76 ++++++++++++++++++++

 sysdeps/x86_64/x32/tst-size_t-wmemcmp.c      | 20 ++++++

 6 files changed, 114 insertions(+), 9 deletions(-)

 create mode 100644 sysdeps/x86_64/x32/tst-size_t-memcmp.c

 create mode 100644 sysdeps/x86_64/x32/tst-size_t-wmemcmp.c

diff --git a/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S b/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S

index 30f764c3..e3a35b89 100644

--- a/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S

+++ b/sysdeps/x86_64/multiarch/memcmp-avx2-movbe.S

@@ -58,9 +58,12 @@

 	.section .text.avx,"ax",@progbits

 ENTRY (MEMCMP)

 # ifdef USE_AS_WMEMCMP

-	shl	$2, %rdx

+	shl	$2, %RDX_LP

+# elif defined __ILP32__

+	/* Clear the upper 32 bits.  */

+	movl	%edx, %edx

 # endif

-	cmpq	$VEC_SIZE, %rdx

+	cmp	$VEC_SIZE, %RDX_LP

 	jb	L(less_vec)

 	/* From VEC to 2 * VEC.  No branch when size == VEC_SIZE.  */

diff --git a/sysdeps/x86_64/multiarch/memcmp-sse4.S b/sysdeps/x86_64/multiarch/memcmp-sse4.S

index 8e164f2c..302900f5 100644

--- a/sysdeps/x86_64/multiarch/memcmp-sse4.S

+++ b/sysdeps/x86_64/multiarch/memcmp-sse4.S

@@ -42,13 +42,16 @@

 	.section .text.sse4.1,"ax",@progbits

 ENTRY (MEMCMP)

 # ifdef USE_AS_WMEMCMP

-	shl	$2, %rdx

+	shl	$2, %RDX_LP

+# elif defined __ILP32__

+	/* Clear the upper 32 bits.  */

+	mov	%edx, %edx

 # endif

 	pxor	%xmm0, %xmm0

-	cmp	$79, %rdx

+	cmp	$79, %RDX_LP

 	ja	L(79bytesormore)

 # ifndef USE_AS_WMEMCMP

-	cmp	$1, %rdx

+	cmp	$1, %RDX_LP

 	je	L(firstbyte)

 # endif

 	add	%rdx, %rsi

diff --git a/sysdeps/x86_64/multiarch/memcmp-ssse3.S b/sysdeps/x86_64/multiarch/memcmp-ssse3.S

index 6f76c641..69d030fc 100644

--- a/sysdeps/x86_64/multiarch/memcmp-ssse3.S

+++ b/sysdeps/x86_64/multiarch/memcmp-ssse3.S

@@ -33,9 +33,12 @@

 	atom_text_section

 ENTRY (MEMCMP)

 # ifdef USE_AS_WMEMCMP

-	shl	$2, %rdx

-	test	%rdx, %rdx

+	shl	$2, %RDX_LP

+	test	%RDX_LP, %RDX_LP

 	jz	L(equal)

+# elif defined __ILP32__

+	/* Clear the upper 32 bits.  */

+	mov	%edx, %edx

 # endif

 	mov	%rdx, %rcx

 	mov	%rdi, %rdx

diff --git a/sysdeps/x86_64/x32/Makefile b/sysdeps/x86_64/x32/Makefile

index 7d528889..ddec7f04 100644

--- a/sysdeps/x86_64/x32/Makefile

+++ b/sysdeps/x86_64/x32/Makefile

@@ -6,9 +6,9 @@ CFLAGS-s_llround.c += -fno-builtin-lround

 endif

 ifeq ($(subdir),string)

-tests += tst-size_t-memchr

+tests += tst-size_t-memchr tst-size_t-memcmp

 endif

 ifeq ($(subdir),wcsmbs)

-tests += tst-size_t-wmemchr

+tests += tst-size_t-wmemchr tst-size_t-wmemcmp

 endif

diff --git a/sysdeps/x86_64/x32/tst-size_t-memcmp.c b/sysdeps/x86_64/x32/tst-size_t-memcmp.c

new file mode 100644

index 00000000..9bd6fdb4

--- /dev/null

+++ b/sysdeps/x86_64/x32/tst-size_t-memcmp.c

@@ -0,0 +1,76 @@

+/* Test memcmp 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

+#ifdef WIDE

+# define TEST_NAME "wmemcmp"

+#else

+# define TEST_NAME "memcmp"

+#endif

+

+#include "test-size_t.h"

+

+#ifdef WIDE

+# include <inttypes.h>

+# include <wchar.h>

+

+# define MEMCMP wmemcmp

+# define CHAR wchar_t

+#else

+# define MEMCMP memcmp

+# define CHAR char

+#endif

+

+IMPL (MEMCMP, 1)

+

+typedef int (*proto_t) (const CHAR *, const CHAR *, size_t);

+

+static int

+__attribute__ ((noinline, noclone))

+do_memcmp (parameter_t a, parameter_t b)

+{

+  return CALL (&b, a.p, b.p, a.len);

+}

+

+static int

+test_main (void)

+{

+  test_init ();

+

+  parameter_t dest = { { page_size / sizeof (CHAR) }, buf1 };

+  parameter_t src = { { 0 }, buf2 };

+

+  memcpy (buf1, buf2, page_size);

+

+  int ret = 0;

+  FOR_EACH_IMPL (impl, 0)

+    {

+      src.fn = impl->fn;

+      int res = do_memcmp (dest, src);

+      if (res)

+	{

+	  error (0, 0, "Wrong result in function %s: %i != 0",

+		 impl->name, res);

+	  ret = 1;

+	}

+    }

+

+  return ret ? EXIT_FAILURE : EXIT_SUCCESS;

+}

+

+#include <support/test-driver.c>

diff --git a/sysdeps/x86_64/x32/tst-size_t-wmemcmp.c b/sysdeps/x86_64/x32/tst-size_t-wmemcmp.c

new file mode 100644

index 00000000..e8b5ffd0

--- /dev/null

+++ b/sysdeps/x86_64/x32/tst-size_t-wmemcmp.c

@@ -0,0 +1,20 @@

+/* Test wmemcmp 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 WIDE 1

+#include "tst-size_t-memcmp.c"

-- 

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