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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-avx2.S: Use RDX_LP for length.
	* sysdeps/x86_64/multiarch/strcpy-sse2-unaligned.S: Likewise.
	* 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.
This commit is contained in:
H.J. Lu 2019-01-21 11:35:18 -08:00
parent ee915088a0
commit c7c54f65b0
6 changed files with 76 additions and 8 deletions
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10
ChangeLog
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@ -1,3 +1,13 @@
2019-01-21 H.J. Lu <hongjiu.lu@intel.com>
[BZ# 24097]
CVE-2019-6488
* sysdeps/x86_64/multiarch/strcpy-avx2.S: Use RDX_LP for length.
* sysdeps/x86_64/multiarch/strcpy-sse2-unaligned.S: Likewise.
* 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.
2019-01-21 H.J. Lu <hongjiu.lu@intel.com>
[BZ# 24097]

4
sysdeps/x86_64/multiarch/strcpy-avx2.S
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@ -49,8 +49,8 @@
.section .text.avx,"ax",@progbits
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

4
sysdeps/x86_64/multiarch/strcpy-sse2-unaligned.S
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@ -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

6
sysdeps/x86_64/multiarch/strcpy-ssse3.S
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@ -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)

2
sysdeps/x86_64/x32/Makefile
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@ -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)

58
sysdeps/x86_64/x32/tst-size_t-strncpy.c Normal file
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@ -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>