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0262507918
These unmangled function pointers reside on the heap and could
be targeted by exploit writers, effectively bypassing libio vtable
validation. Instead, we ignore these pointers and always call
malloc or free.
In theory, this is a backwards-incompatible change, but using the
global heap instead of the user-supplied callback functions should
have little application impact. (The old libstdc++ implementation
exposed this functionality via a public, undocumented constructor
in its strstreambuf class.)
(cherry picked from commit 4e8a6346cd)
89 lines
3.2 KiB
C
89 lines
3.2 KiB
C
/* Copyright (C) 1995-2018 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>.
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As a special exception, if you link the code in this file with
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files compiled with a GNU compiler to produce an executable,
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that does not cause the resulting executable to be covered by
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the GNU Lesser General Public License. This exception does not
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however invalidate any other reasons why the executable file
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might be covered by the GNU Lesser General Public License.
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This exception applies to code released by its copyright holders
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in files containing the exception. */
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#include <malloc.h>
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#include <string.h>
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#include "libioP.h"
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#include "stdio.h"
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#include <stdio_ext.h>
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#include "strfile.h"
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int
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_IO_vasprintf (char **result_ptr, const char *format, _IO_va_list args)
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{
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/* Initial size of the buffer to be used. Will be doubled each time an
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overflow occurs. */
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const _IO_size_t init_string_size = 100;
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char *string;
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_IO_strfile sf;
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int ret;
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_IO_size_t needed;
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_IO_size_t allocated;
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/* No need to clear the memory here (unlike for open_memstream) since
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we know we will never seek on the stream. */
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string = (char *) malloc (init_string_size);
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if (string == NULL)
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return -1;
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#ifdef _IO_MTSAFE_IO
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sf._sbf._f._lock = NULL;
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#endif
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_IO_no_init (&sf._sbf._f, _IO_USER_LOCK, -1, NULL, NULL);
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_IO_JUMPS (&sf._sbf) = &_IO_str_jumps;
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_IO_str_init_static_internal (&sf, string, init_string_size, string);
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sf._sbf._f._flags &= ~_IO_USER_BUF;
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sf._s._allocate_buffer_unused = (_IO_alloc_type) malloc;
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sf._s._free_buffer_unused = (_IO_free_type) free;
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ret = _IO_vfprintf (&sf._sbf._f, format, args);
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if (ret < 0)
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{
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free (sf._sbf._f._IO_buf_base);
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return ret;
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}
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/* Only use realloc if the size we need is of the same (binary)
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order of magnitude then the memory we allocated. */
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needed = sf._sbf._f._IO_write_ptr - sf._sbf._f._IO_write_base + 1;
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allocated = sf._sbf._f._IO_write_end - sf._sbf._f._IO_write_base;
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if ((allocated >> 1) <= needed)
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*result_ptr = (char *) realloc (sf._sbf._f._IO_buf_base, needed);
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else
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{
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*result_ptr = (char *) malloc (needed);
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if (*result_ptr != NULL)
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{
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memcpy (*result_ptr, sf._sbf._f._IO_buf_base, needed - 1);
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free (sf._sbf._f._IO_buf_base);
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}
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else
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/* We have no choice, use the buffer we already have. */
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*result_ptr = (char *) realloc (sf._sbf._f._IO_buf_base, needed);
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}
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if (*result_ptr == NULL)
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*result_ptr = sf._sbf._f._IO_buf_base;
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(*result_ptr)[needed - 1] = '\0';
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return ret;
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}
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ldbl_weak_alias (_IO_vasprintf, vasprintf)
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