c6a96a8441
Prior to this commit, fread/fwrite calls with size * nmemb > SIZE_MAX were handled by reading or writing (size_t)(size * nmemb) bytes; for example, on 32-bit platforms, fread(ptr, 641, 6700417, f) would read 1 byte and indicate that the requested 6700417 blocks had been read. This commit adds a check for such integer overflows, and treats them as if an overly large request was passed to read/write; i.e., it sets errno to EINVAL, sets the error indicator on the file, and returns a short object count (0, to be specific). The overflow check involves an integer division, so as a performance optimization we check first to see if both size and nmemb are less than 2^16; if they are, no overflow is possible and we avoid the division. We assume here that size_t is at least 32 bits; this appears to be true on all platforms FreeBSD supports. Although this commit fixes an integer overflow, it is not likely to have any security implications, since any program which would be affected by this bug fix is quite clearly already very confused. Reviewed by: kib MFC after: 1 month
100 lines
3.2 KiB
C
100 lines
3.2 KiB
C
/*-
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* Copyright (c) 1990, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Chris Torek.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#if defined(LIBC_SCCS) && !defined(lint)
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static char sccsid[] = "@(#)fwrite.c 8.1 (Berkeley) 6/4/93";
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#endif /* LIBC_SCCS and not lint */
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#include <sys/cdefs.h>
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__FBSDID("$FreeBSD$");
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#include "namespace.h"
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#include <errno.h>
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#include <stdint.h>
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#include <stdio.h>
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#include "un-namespace.h"
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#include "local.h"
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#include "fvwrite.h"
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#include "libc_private.h"
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/*
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* Write `count' objects (each size `size') from memory to the given file.
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* Return the number of whole objects written.
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*/
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size_t
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fwrite(buf, size, count, fp)
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const void * __restrict buf;
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size_t size, count;
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FILE * __restrict fp;
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{
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size_t n;
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struct __suio uio;
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struct __siov iov;
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/*
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* ANSI and SUSv2 require a return value of 0 if size or count are 0.
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*/
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if ((count == 0) || (size == 0))
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return (0);
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/*
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* Check for integer overflow. As an optimization, first check that
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* at least one of {count, size} is at least 2^16, since if both
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* values are less than that, their product can't possible overflow
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* (size_t is always at least 32 bits on FreeBSD).
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*/
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if (((count | size) > 0xFFFF) &&
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(count > SIZE_MAX / size)) {
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errno = EINVAL;
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fp->_flags |= __SERR;
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return (0);
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}
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n = count * size;
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iov.iov_base = (void *)buf;
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uio.uio_resid = iov.iov_len = n;
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uio.uio_iov = &iov;
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uio.uio_iovcnt = 1;
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FLOCKFILE(fp);
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ORIENT(fp, -1);
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/*
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* The usual case is success (__sfvwrite returns 0);
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* skip the divide if this happens, since divides are
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* generally slow and since this occurs whenever size==0.
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*/
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if (__sfvwrite(fp, &uio) != 0)
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count = (n - uio.uio_resid) / size;
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FUNLOCKFILE(fp);
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return (count);
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}
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