IABSD.fr/src/lib/libc/stdio/freopen.c

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• Author : deraadt
  Date : 2019-06-29 16:12:21
  Hash : 97f9487f
  Message : two more syscall == -1 checks

• lib/libc/stdio/freopen.c

• /*	$OpenBSD: freopen.c,v 1.17 2019/06/29 16:12:21 deraadt Exp $ */
  /*-
   * 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.
   */
  
  #include <sys/types.h>
  #include <sys/stat.h>
  #include <fcntl.h>
  #include <errno.h>
  #include <limits.h>
  #include <unistd.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include "local.h"
  
  /* 
   * Re-direct an existing, open (probably) file to some other file. 
   * ANSI is written such that the original file gets closed if at
   * all possible, no matter what.
   */
  FILE *
  freopen(const char *file, const char *mode, FILE *fp)
  {
  	int f;
  	int flags, isopen, oflags, sverrno, wantfd;
  
  	if ((flags = __sflags(mode, &oflags)) == 0) {
  		(void) fclose(fp);
  		return (NULL);
  	}
  
  	if (!__sdidinit)
  		__sinit();
  
  	FLOCKFILE(fp);
  
  	/*
  	 * There are actually programs that depend on being able to "freopen"
  	 * descriptors that weren't originally open.  Keep this from breaking.
  	 * Remember whether the stream was open to begin with, and which file
  	 * descriptor (if any) was associated with it.  If it was attached to
  	 * a descriptor, defer closing it; freopen("/dev/stdin", "r", stdin)
  	 * should work.  This is unnecessary if it was not a Unix file.
  	 */
  	if (fp->_flags == 0) {
  		fp->_flags = __SEOF;	/* hold on to it */
  		isopen = 0;
  		wantfd = -1;
  	} else {
  		/* flush the stream; ANSI doesn't require this. */
  		if (fp->_flags & __SWR)
  			(void) __sflush(fp);
  		/* if close is NULL, closing is a no-op, hence pointless */
  		isopen = fp->_close != NULL;
  		if ((wantfd = fp->_file) < 0 && isopen) {
  			(void) (*fp->_close)(fp->_cookie);
  			isopen = 0;
  		}
  	}
  
  	/* Get a new descriptor to refer to the new file. */
  	f = open(file, oflags, DEFFILEMODE);
  	if (f == -1 && isopen) {
  		/* If out of fd's close the old one and try again. */
  		if (errno == ENFILE || errno == EMFILE) {
  			(void) (*fp->_close)(fp->_cookie);
  			isopen = 0;
  			f = open(file, oflags, DEFFILEMODE);
  		}
  	}
  	sverrno = errno;
  
  	/*
  	 * Finish closing fp.  Even if the open succeeded above, we cannot
  	 * keep fp->_base: it may be the wrong size.  This loses the effect
  	 * of any setbuffer calls, but stdio has always done this before.
  	 */
  	if (isopen && f != wantfd)
  		(void) (*fp->_close)(fp->_cookie);
  	if (fp->_flags & __SMBF)
  		free((char *)fp->_bf._base);
  	fp->_w = 0;
  	fp->_r = 0;
  	fp->_p = NULL;
  	fp->_bf._base = NULL;
  	fp->_bf._size = 0;
  	fp->_lbfsize = 0;
  	if (HASUB(fp))
  		FREEUB(fp);
  	_UB(fp)._size = 0;
  	WCIO_FREE(fp);
  	if (HASLB(fp))
  		FREELB(fp);
  	fp->_lb._size = 0;
  
  	if (f == -1) {			/* did not get it after all */
  		fp->_flags = 0;		/* set it free */
  		FUNLOCKFILE(fp);
  		errno = sverrno;	/* restore in case _close clobbered */
  		return (NULL);
  	}
  
  	/*
  	 * If reopening something that was open before on a real file, try
  	 * to maintain the descriptor.  Various C library routines (perror)
  	 * assume stderr is always fd STDERR_FILENO, even if being freopen'd.
  	 */
  	if (wantfd >= 0 && f != wantfd) {
  		if (dup3(f, wantfd, oflags & O_CLOEXEC) >= 0) {
  			(void) close(f);
  			f = wantfd;
  		}
  	}
  
  	/* _file is only a short */
  	if (f > SHRT_MAX) {
  		fp->_flags = 0;		/* set it free */
  		FUNLOCKFILE(fp);
  		errno = EMFILE;
  		return (NULL);
  	}
  
  	fp->_flags = flags;
  	fp->_file = f;
  	fp->_cookie = fp;
  	fp->_read = __sread;
  	fp->_write = __swrite;
  	fp->_seek = __sseek;
  	fp->_close = __sclose;
  
  	/*
  	 * When opening in append mode, even though we use O_APPEND,
  	 * we need to seek to the end so that ftell() gets the right
  	 * answer.  If the user then alters the seek pointer, or
  	 * the file extends, this will fail, but there is not much
  	 * we can do about this.  (We could set __SAPP and check in
  	 * fseek and ftell.)
  	 */
  	if (oflags & O_APPEND)
  		(void) __sseek(fp, 0, SEEK_END);
  	FUNLOCKFILE(fp);
  	return (fp);
  }
  DEF_STRONG(freopen);