From c62e1cf68a70de8ac4cc8aebae760784009777c5 Mon Sep 17 00:00:00 2001

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

Date: Fri, 1 Feb 2019 12:20:54 -0800

Subject: [PATCH] x86-64 memrchr: 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 memrchr 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/memrchr.S: Use RDX_LP for length.

	* sysdeps/x86_64/multiarch/memrchr-avx2.S: Likewise.

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

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

(cherry picked from commit ecd8b842cf37ea112e59cd9085ff1f1b6e208ae0)

---

 sysdeps/x86_64/memrchr.S                |  4 +-

 sysdeps/x86_64/multiarch/memrchr-avx2.S |  4 +-

 sysdeps/x86_64/x32/Makefile             |  3 +-

 sysdeps/x86_64/x32/tst-size_t-memrchr.c | 57 +++++++++++++++++++++++++

 4 files changed, 63 insertions(+), 5 deletions(-)

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

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

index b8e3fa1d..dc82f8f7 100644

--- a/sysdeps/x86_64/memrchr.S

+++ b/sysdeps/x86_64/memrchr.S

@@ -24,13 +24,13 @@

 ENTRY (__memrchr)

 	movd	%esi, %xmm1

-	sub	$16, %rdx

+	sub	$16, %RDX_LP

 	jbe	L(length_less16)

 	punpcklbw	%xmm1, %xmm1

 	punpcklbw	%xmm1, %xmm1

-	add	%rdx, %rdi

+	add	%RDX_LP, %RDI_LP

 	pshufd	$0, %xmm1, %xmm1

 	movdqu	(%rdi), %xmm0

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

index b41a58bc..ce488dd9 100644

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

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

@@ -32,10 +32,10 @@ ENTRY (__memrchr_avx2)

 	vmovd	%esi, %xmm0

 	vpbroadcastb %xmm0, %ymm0

-	subq	$VEC_SIZE, %rdx

+	sub	$VEC_SIZE, %RDX_LP

 	jbe	L(last_vec_or_less)

-	addq	%rdx, %rdi

+	add	%RDX_LP, %RDI_LP

 	/* Check the last VEC_SIZE bytes.  */

 	vpcmpeqb (%rdi), %ymm0, %ymm1

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

index 2fe1e5ac..e99dbd7c 100644

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

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

@@ -6,7 +6,8 @@ CFLAGS-s_llround.c += -fno-builtin-lround

 endif

 ifeq ($(subdir),string)

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

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

+	 tst-size_t-memrchr

 endif

 ifeq ($(subdir),wcsmbs)

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

new file mode 100644

index 00000000..c83699c0

--- /dev/null

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

@@ -0,0 +1,57 @@

+/* Test memrchr 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 "memrchr"

+#include "test-size_t.h"

+

+IMPL (memchr, 1)

+

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

+

+static void *

+__attribute__ ((noinline, noclone))

+do_memrchr (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 }, buf2 };

+  parameter_t c = { { 0 }, (void *) (uintptr_t) 0x12 };

+

+  int ret = 0;

+  FOR_EACH_IMPL (impl, 0)

+    {

+      c.fn = impl->fn;

+      void * res = do_memrchr (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 <support/test-driver.c>

-- 

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