From 4f97e8708512462e87d2f1f1bdeb8cf55ce10e5a Mon Sep 17 00:00:00 2001

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

Date: Fri, 1 Feb 2019 12:23:23 -0800

Subject: [PATCH] x86-64 strncpy: 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 strncpy 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/strcpy-sse2-unaligned.S: Use RDX_LP

	for length.

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

	* sysdeps/x86_64/x32/Makefile (tests): Add tst-size_t-strncpy.

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

(cherry picked from commit c7c54f65b080affb87a1513dee449c8ad6143c8b)

---

 .../x86_64/multiarch/strcpy-sse2-unaligned.S  |  4 +-

 sysdeps/x86_64/multiarch/strcpy-ssse3.S       |  6 +-

 sysdeps/x86_64/x32/Makefile                   |  2 +-

 sysdeps/x86_64/x32/tst-size_t-strncpy.c       | 58 +++++++++++++++++++

 4 files changed, 64 insertions(+), 6 deletions(-)

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

diff --git a/sysdeps/x86_64/multiarch/strcpy-sse2-unaligned.S b/sysdeps/x86_64/multiarch/strcpy-sse2-unaligned.S

index 72bf7e85..50aca22d 100644

--- a/sysdeps/x86_64/multiarch/strcpy-sse2-unaligned.S

+++ b/sysdeps/x86_64/multiarch/strcpy-sse2-unaligned.S

@@ -40,8 +40,8 @@

 .text

 ENTRY (STRCPY)

 #  ifdef USE_AS_STRNCPY

-	mov	%rdx, %r8

-	test	%r8, %r8

+	mov	%RDX_LP, %R8_LP

+	test	%R8_LP, %R8_LP

 	jz	L(ExitZero)

 #  endif

 	mov	%rsi, %rcx

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

index 9858d0c4..0a62814a 100644

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

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

@@ -31,13 +31,13 @@ ENTRY (STRCPY)

 	mov	%rsi, %rcx

 #  ifdef USE_AS_STRNCPY

-	mov	%rdx, %r8

+	mov	%RDX_LP, %R8_LP

 #  endif

 	mov	%rdi, %rdx

 #  ifdef USE_AS_STRNCPY

-	test	%r8, %r8

+	test	%R8_LP, %R8_LP

 	jz	L(Exit0)

-	cmp	$8, %r8

+	cmp	$8, %R8_LP

 	jbe	L(StrncpyExit8Bytes)

 # endif

 	cmpb	$0, (%rcx)

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

index db302839..2a9e20a9 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-strncmp tst-size_t-strncpy

 endif

 ifeq ($(subdir),wcsmbs)

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

new file mode 100644

index 00000000..4dec71e6

--- /dev/null

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

@@ -0,0 +1,58 @@

+/* Test strncpy 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_NAME "strncpy"

+#include "test-size_t.h"

+

+IMPL (strncpy, 1)

+

+typedef char *(*proto_t) (char *, const char*, size_t);

+

+static void *

+__attribute__ ((noinline, noclone))

+do_strncpy (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 }, buf1 };

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

+

+  int ret = 0;

+  FOR_EACH_IMPL (impl, 0)

+    {

+      src.fn = impl->fn;

+      do_strncpy (dest, src);

+      int res = strncmp (dest.p, src.p, dest.len);

+      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>

-- 

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