1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 2007-2009 Dag-Erling Coïdan 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 __FBSDID("$FreeBSD$"); 32 33 #include <sys/file.h> 34 #include <sys/stat.h> 35 36 #include <errno.h> 37 #include <stdarg.h> 38 #include <unistd.h> 39 40 #include <libutil.h> 41 42 /* 43 * Reliably open and lock a file. 44 * 45 * Please do not modify this code without first reading the revision history 46 * and discussing your changes with <des@freebsd.org>. Don't be fooled by the 47 * code's apparent simplicity; there would be no need for this function if it 48 * was easy to get right. 49 */ 50 static int 51 vflopenat(int dirfd, const char *path, int flags, va_list ap) 52 { 53 int fd, operation, serrno, trunc; 54 struct stat sb, fsb; 55 mode_t mode; 56 57 #ifdef O_EXLOCK 58 flags &= ~O_EXLOCK; 59 #endif 60 61 mode = 0; 62 if (flags & O_CREAT) { 63 mode = (mode_t)va_arg(ap, int); /* mode_t promoted to int */ 64 } 65 66 operation = LOCK_EX; 67 if (flags & O_NONBLOCK) 68 operation |= LOCK_NB; 69 70 trunc = (flags & O_TRUNC); 71 flags &= ~O_TRUNC; 72 73 for (;;) { 74 if ((fd = openat(dirfd, path, flags, mode)) == -1) 75 /* non-existent or no access */ 76 return (-1); 77 if (flock(fd, operation) == -1) { 78 /* unsupported or interrupted */ 79 serrno = errno; 80 (void)close(fd); 81 errno = serrno; 82 return (-1); 83 } 84 if (fstatat(dirfd, path, &sb, 0) == -1) { 85 /* disappeared from under our feet */ 86 (void)close(fd); 87 continue; 88 } 89 if (fstat(fd, &fsb) == -1) { 90 /* can't happen [tm] */ 91 serrno = errno; 92 (void)close(fd); 93 errno = serrno; 94 return (-1); 95 } 96 if (sb.st_dev != fsb.st_dev || 97 sb.st_ino != fsb.st_ino) { 98 /* changed under our feet */ 99 (void)close(fd); 100 continue; 101 } 102 if (trunc && ftruncate(fd, 0) != 0) { 103 /* can't happen [tm] */ 104 serrno = errno; 105 (void)close(fd); 106 errno = serrno; 107 return (-1); 108 } 109 /* 110 * The following change is provided as a specific example to 111 * avoid. 112 */ 113 #if 0 114 if (fcntl(fd, F_SETFD, FD_CLOEXEC) != 0) { 115 serrno = errno; 116 (void)close(fd); 117 errno = serrno; 118 return (-1); 119 } 120 #endif 121 return (fd); 122 } 123 } 124 125 int 126 flopen(const char *path, int flags, ...) 127 { 128 va_list ap; 129 int ret; 130 131 va_start(ap, flags); 132 ret = vflopenat(AT_FDCWD, path, flags, ap); 133 va_end(ap); 134 return (ret); 135 } 136 137 int 138 flopenat(int dirfd, const char *path, int flags, ...) 139 { 140 va_list ap; 141 int ret; 142 143 va_start(ap, flags); 144 ret = vflopenat(dirfd, path, flags, ap); 145 va_end(ap); 146 return (ret); 147 } 148