freebsd-dev/lib/libc/stdio/fflush.c
Xin LI 805288c2f0 In r268924 __fflush was modified so that when write(2) was not successful,
_p and _w are adjusted to account for the partial write (if any).

However, _p and _w should not be unconditionally adjusted and should only
be changed when we actually wrote some bytes, or the accumulated accounting
error will eventually result in a heap buffer overflow.

Reported by:	adrian and alfred (Norse Corporation)
Security:	FreeBSD-SA-14:27.stdio
Security:	CVE-2014-8611
2014-12-10 08:18:22 +00:00

151 lines
4.0 KiB
C

/*-
* Copyright (c) 1990, 1993
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Chris Torek.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)fflush.c 8.1 (Berkeley) 6/4/93";
#endif /* LIBC_SCCS and not lint */
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "namespace.h"
#include <errno.h>
#include <stdio.h>
#include "un-namespace.h"
#include "libc_private.h"
#include "local.h"
static int sflush_locked(FILE *);
/*
* Flush a single file, or (if fp is NULL) all files.
* MT-safe version
*/
int
fflush(FILE *fp)
{
int retval;
if (fp == NULL)
return (_fwalk(sflush_locked));
FLOCKFILE(fp);
/*
* There is disagreement about the correct behaviour of fflush()
* when passed a file which is not open for writing. According to
* the ISO C standard, the behaviour is undefined.
* Under linux, such an fflush returns success and has no effect;
* under Windows, such an fflush is documented as behaving instead
* as fpurge().
* Given that applications may be written with the expectation of
* either of these two behaviours, the only safe (non-astonishing)
* option is to return EBADF and ask that applications be fixed.
* SUSv3 now requires that fflush() returns success on a read-only
* stream.
*
*/
if ((fp->_flags & (__SWR | __SRW)) == 0)
retval = 0;
else
retval = __sflush(fp);
FUNLOCKFILE(fp);
return (retval);
}
/*
* Flush a single file, or (if fp is NULL) all files.
* Non-MT-safe version
*/
int
__fflush(FILE *fp)
{
int retval;
if (fp == NULL)
return (_fwalk(sflush_locked));
if ((fp->_flags & (__SWR | __SRW)) == 0)
retval = 0;
else
retval = __sflush(fp);
return (retval);
}
int
__sflush(FILE *fp)
{
unsigned char *p;
int n, t;
t = fp->_flags;
if ((t & __SWR) == 0)
return (0);
if ((p = fp->_bf._base) == NULL)
return (0);
n = fp->_p - p; /* write this much */
/*
* Set these immediately to avoid problems with longjmp and to allow
* exchange buffering (via setvbuf) in user write function.
*/
fp->_p = p;
fp->_w = t & (__SLBF|__SNBF) ? 0 : fp->_bf._size;
for (; n > 0; n -= t, p += t) {
t = _swrite(fp, (char *)p, n);
if (t <= 0) {
/* Reset _p and _w. */
if (p > fp->_p) {
/* Some was written. */
memmove(fp->_p, p, n);
fp->_p += n;
if ((fp->_flags & (__SLBF | __SNBF)) == 0)
fp->_w -= n;
}
fp->_flags |= __SERR;
return (EOF);
}
}
return (0);
}
static int
sflush_locked(FILE *fp)
{
int ret;
FLOCKFILE(fp);
ret = __sflush(fp);
FUNLOCKFILE(fp);
return (ret);
}