From 3e2556a4407e551a9c4086e67f46ef8d235cfe0d Mon Sep 17 00:00:00 2001

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

Date: Fri, 1 Feb 2019 12:24:08 -0800

Subject: [PATCH] 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/multiarch/strlen-avx2.S: Use RSI_LP for length.

	Clear the upper 32 bits of RSI register.

	* sysdeps/x86_64/strlen.S: Use RSI_LP for length.

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

	and tst-size_t-wcsnlen.

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

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

(cherry picked from commit 5165de69c0908e28a380cbd4bb054e55ea4abc95)

---

 sysdeps/x86_64/multiarch/strlen-avx2.S  |  9 ++--

 sysdeps/x86_64/strlen.S                 | 12 ++---

 sysdeps/x86_64/x32/Makefile             |  4 +-

 sysdeps/x86_64/x32/tst-size_t-strnlen.c | 72 +++++++++++++++++++++++++

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

 5 files changed, 106 insertions(+), 11 deletions(-)

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

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

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

index fb2418cd..645e0446 100644

--- a/sysdeps/x86_64/multiarch/strlen-avx2.S

+++ b/sysdeps/x86_64/multiarch/strlen-avx2.S

@@ -42,12 +42,15 @@

 ENTRY (STRLEN)

 # ifdef USE_AS_STRNLEN

 	/* Check for zero length.  */

-	testq	%rsi, %rsi

+	test	%RSI_LP, %RSI_LP

 	jz	L(zero)

 #  ifdef USE_AS_WCSLEN

-	shl	$2, %rsi

+	shl	$2, %RSI_LP

+#  elif defined __ILP32__

+	/* Clear the upper 32 bits.  */

+	movl	%esi, %esi

 #  endif

-	movq	%rsi, %r8

+	mov	%RSI_LP, %R8_LP

 # endif

 	movl	%edi, %ecx

 	movq	%rdi, %rdx

diff --git a/sysdeps/x86_64/strlen.S b/sysdeps/x86_64/strlen.S

index 01cb5fa8..f845f3d4 100644

--- a/sysdeps/x86_64/strlen.S

+++ b/sysdeps/x86_64/strlen.S

@@ -59,21 +59,21 @@ ENTRY(strlen)

 #ifdef AS_STRNLEN

 /* Do not read anything when n==0.  */

-	test	%rsi, %rsi

+	test	%RSI_LP, %RSI_LP

 	jne	L(n_nonzero)

 	xor	%rax, %rax

 	ret

 L(n_nonzero):

 # ifdef AS_WCSLEN

-	shlq	$2, %rsi

+	shl	$2, %RSI_LP

 # endif

 /* Initialize long lived registers.  */

-	add	%rdi, %rsi

-	mov	%rsi, %r10

-	and	$-64, %r10

-	mov	%rsi, %r11

+	add	%RDI_LP, %RSI_LP

+	mov	%RSI_LP, %R10_LP

+	and	$-64, %R10_LP

+	mov	%RSI_LP, %R11_LP

 #endif

 	pxor	%xmm0, %xmm0

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

index 2a9e20a9..1557724b 100644

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

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

@@ -8,10 +8,10 @@ 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)

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

-	 tst-size_t-wcsncmp

+	 tst-size_t-wcsncmp tst-size_t-wcsnlen

 endif

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 00000000..690a4a8a

--- /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 <support/test-driver.c>

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

new file mode 100644

index 00000000..093b4bbe

--- /dev/null

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

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

+/* Test wcsnlen 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-strnlen.c"

-- 

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