6f201b686b
On the first call to fread(3), just after fopen(3) the internal buffers are empty. This means that _r and _p (among others) are zeroed. Passing NULL to the 2nd argument of memcpy(3) for the zero length is undefined. Calling _p += 0 triggers LLVM UBSan (NULL pointer arithmetic). Calling _p += 0, p += 0 and resid -= 0 has no effect. Replace the "fp->_r = 0;" logic with a short circuit jump to __srefill() that sets _r internally and refills the FILE buffers. No functional change from an end user point of view, except skipping a few dummy operations on the first call, for a FILE pointer, to fread(3).
100 lines
3.0 KiB
C
100 lines
3.0 KiB
C
/* $NetBSD: fread.c,v 1.23 2020/02/22 22:02:46 kamil Exp $ */
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/*-
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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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* 3. 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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#include <sys/cdefs.h>
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#if defined(LIBC_SCCS) && !defined(lint)
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#if 0
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static char sccsid[] = "@(#)fread.c 8.2 (Berkeley) 12/11/93";
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#else
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__RCSID("$NetBSD: fread.c,v 1.23 2020/02/22 22:02:46 kamil Exp $");
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#endif
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#endif /* LIBC_SCCS and not lint */
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#include <assert.h>
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#include <errno.h>
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#include <stdio.h>
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#include <string.h>
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#include "reentrant.h"
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#include "local.h"
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size_t
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fread(void *buf, size_t size, size_t count, FILE *fp)
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{
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size_t resid;
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char *p;
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int r;
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size_t total;
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_DIAGASSERT(fp != NULL);
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/*
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* The ANSI standard requires a return value of 0 for a count
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* or a size of 0. Whilst ANSI imposes no such requirements on
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* fwrite, the SUSv2 does.
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*/
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if ((resid = count * size) == 0)
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return 0;
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_DIAGASSERT(buf != NULL);
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FLOCKFILE(fp);
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total = resid;
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p = buf;
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if (fp->_r <= 0) {
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/* Nothing to read on enter, refill the buffers. */
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goto refill;
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}
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while (resid > (size_t)(r = fp->_r)) {
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(void)memcpy(p, fp->_p, (size_t)r);
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fp->_p += r;
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/* fp->_r = 0 ... done in __srefill */
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p += r;
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resid -= r;
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refill:
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if (__srefill(fp)) {
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/* no more input: return partial result */
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FUNLOCKFILE(fp);
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return (total - resid) / size;
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}
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}
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(void)memcpy(p, fp->_p, resid);
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_DIAGASSERT(__type_fit(int, fp->_r - resid));
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fp->_r -= (int)resid;
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fp->_p += resid;
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FUNLOCKFILE(fp);
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return count;
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}
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