db3476aff1
This commit puts all libio vtables in a dedicated, read-only ELF section, so that they are consecutive in memory. Before any indirect jump, the vtable pointer is checked against the section boundaries, and the process is terminated if the vtable pointer does not fall into the special ELF section. To enable backwards compatibility, a special flag variable (_IO_accept_foreign_vtables), protected by the pointer guard, avoids process termination if libio stream object constructor functions have been called earlier. Such constructor functions are called by the GCC 2.95 libstdc++ library, and this mechanism ensures compatibility with old binaries. Existing callers inside glibc of these functions are adjusted to call the original functions, not the wrappers which enable vtable compatiblity. The compatibility mechanism is used to enable passing FILE * objects across a static dlopen boundary, too.
71 lines
2.4 KiB
C
71 lines
2.4 KiB
C
/* Copyright (C) 1991-2016 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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#include <stdarg.h>
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#include <stdio.h>
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#include "../libio/libioP.h"
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#include "../libio/strfile.h"
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extern const struct _IO_jump_t _IO_strn_jumps libio_vtable attribute_hidden;
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/* Write formatted output into S, according to the format
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string FORMAT, writing no more than MAXLEN characters. */
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/* VARARGS5 */
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int
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___vsnprintf_chk (char *s, size_t maxlen, int flags, size_t slen,
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const char *format, va_list args)
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{
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/* XXX Maybe for less strict version do not fail immediately.
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Though, maxlen is supposed to be the size of buffer pointed
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to by s, so a conforming program can't pass such maxlen
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to *snprintf. */
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if (__glibc_unlikely (slen < maxlen))
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__chk_fail ();
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_IO_strnfile sf;
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int ret;
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#ifdef _IO_MTSAFE_IO
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sf.f._sbf._f._lock = NULL;
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#endif
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/* We need to handle the special case where MAXLEN is 0. Use the
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overflow buffer right from the start. */
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if (maxlen == 0)
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{
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s = sf.overflow_buf;
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maxlen = sizeof (sf.overflow_buf);
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}
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_IO_no_init (&sf.f._sbf._f, _IO_USER_LOCK, -1, NULL, NULL);
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_IO_JUMPS (&sf.f._sbf) = &_IO_strn_jumps;
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s[0] = '\0';
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/* For flags > 0 (i.e. __USE_FORTIFY_LEVEL > 1) request that %n
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can only come from read-only format strings. */
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if (flags > 0)
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sf.f._sbf._f._flags2 |= _IO_FLAGS2_FORTIFY;
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_IO_str_init_static_internal (&sf.f, s, maxlen - 1, s);
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ret = _IO_vfprintf (&sf.f._sbf._f, format, args);
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if (sf.f._sbf._f._IO_buf_base != sf.overflow_buf)
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*sf.f._sbf._f._IO_write_ptr = '\0';
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return ret;
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}
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ldbl_hidden_def (___vsnprintf_chk, __vsnprintf_chk)
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ldbl_strong_alias (___vsnprintf_chk, __vsnprintf_chk)
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