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4e8a6346cd
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.)
83 lines
2.7 KiB
C
83 lines
2.7 KiB
C
/* Copyright (C) 1993-2018 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 <stdio.h>
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#include "libioP.h"
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typedef void *(*_IO_alloc_type) (size_t);
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typedef void (*_IO_free_type) (void*);
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struct _IO_str_fields
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{
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/* These members are preserved for ABI compatibility. The glibc
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implementation always calls malloc/free for user buffers if
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_IO_USER_BUF or _IO_FLAGS2_USER_WBUF are not set. */
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_IO_alloc_type _allocate_buffer_unused;
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_IO_free_type _free_buffer_unused;
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};
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/* This is needed for the Irix6 N32 ABI, which has a 64 bit off_t type,
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but a 32 bit pointer type. In this case, we get 4 bytes of padding
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after the vtable pointer. Putting them in a structure together solves
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this problem. */
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struct _IO_streambuf
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{
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FILE _f;
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const struct _IO_jump_t *vtable;
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};
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typedef struct _IO_strfile_
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{
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struct _IO_streambuf _sbf;
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struct _IO_str_fields _s;
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} _IO_strfile;
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/* frozen: set when the program has requested that the array object not
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be altered, reallocated, or freed. */
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#define _IO_STR_FROZEN(FP) ((FP)->_f._flags & _IO_USER_BUF)
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typedef struct
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{
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_IO_strfile f;
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/* This is used for the characters which do not fit in the buffer
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provided by the user. */
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char overflow_buf[64];
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} _IO_strnfile;
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extern const struct _IO_jump_t _IO_strn_jumps attribute_hidden;
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typedef struct
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{
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_IO_strfile f;
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/* This is used for the characters which do not fit in the buffer
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provided by the user. */
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wchar_t overflow_buf[64];
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} _IO_wstrnfile;
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extern const struct _IO_jump_t _IO_wstrn_jumps attribute_hidden;
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