1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2007-2009 Dag-Erling Smørgrav 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer 12 * in this position and unchanged. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 */ 29 30 #include <sys/cdefs.h> 31 #include <sys/file.h> 32 #include <sys/stat.h> 33 34 #include <errno.h> 35 #include <stdarg.h> 36 #include <unistd.h> 37 38 #include <libutil.h> 39 40 /* 41 * Reliably open and lock a file. 42 * 43 * Please do not modify this code without first reading the revision history 44 * and discussing your changes with <des@freebsd.org>. Don't be fooled by the 45 * code's apparent simplicity; there would be no need for this function if it 46 * was easy to get right. 47 */ 48 static int 49 vflopenat(int dirfd, const char *path, int flags, va_list ap) 50 { 51 int fd, operation, serrno, trunc; 52 struct stat sb, fsb; 53 mode_t mode; 54 55 #ifdef O_EXLOCK 56 flags &= ~O_EXLOCK; 57 #endif 58 59 mode = 0; 60 if (flags & O_CREAT) { 61 mode = (mode_t)va_arg(ap, int); /* mode_t promoted to int */ 62 } 63 64 operation = LOCK_EX; 65 if (flags & O_NONBLOCK) 66 operation |= LOCK_NB; 67 68 trunc = (flags & O_TRUNC); 69 flags &= ~O_TRUNC; 70 71 for (;;) { 72 if ((fd = openat(dirfd, path, flags, mode)) == -1) 73 /* non-existent or no access */ 74 return (-1); 75 if (flock(fd, operation) == -1) { 76 /* unsupported or interrupted */ 77 serrno = errno; 78 (void)close(fd); 79 errno = serrno; 80 return (-1); 81 } 82 if (fstatat(dirfd, path, &sb, 0) == -1) { 83 /* disappeared from under our feet */ 84 (void)close(fd); 85 continue; 86 } 87 if (fstat(fd, &fsb) == -1) { 88 /* can't happen [tm] */ 89 serrno = errno; 90 (void)close(fd); 91 errno = serrno; 92 return (-1); 93 } 94 if (sb.st_dev != fsb.st_dev || 95 sb.st_ino != fsb.st_ino) { 96 /* changed under our feet */ 97 (void)close(fd); 98 continue; 99 } 100 if (trunc && ftruncate(fd, 0) != 0) { 101 /* can't happen [tm] */ 102 serrno = errno; 103 (void)close(fd); 104 errno = serrno; 105 return (-1); 106 } 107 /* 108 * The following change is provided as a specific example to 109 * avoid. 110 */ 111 #if 0 112 if (fcntl(fd, F_SETFD, FD_CLOEXEC) != 0) { 113 serrno = errno; 114 (void)close(fd); 115 errno = serrno; 116 return (-1); 117 } 118 #endif 119 return (fd); 120 } 121 } 122 123 int 124 flopen(const char *path, int flags, ...) 125 { 126 va_list ap; 127 int ret; 128 129 va_start(ap, flags); 130 ret = vflopenat(AT_FDCWD, path, flags, ap); 131 va_end(ap); 132 return (ret); 133 } 134 135 int 136 flopenat(int dirfd, const char *path, int flags, ...) 137 { 138 va_list ap; 139 int ret; 140 141 va_start(ap, flags); 142 ret = vflopenat(dirfd, path, flags, ap); 143 va_end(ap); 144 return (ret); 145 } 146