lib/replace/closefrom.c

   1 /*
   2  * Unix SMB/CIFS implementation.
   3  * Samba utility functions
   4  * Copyright (C) Volker Lendecke 2016
   5  *
   6  *   ** NOTE! The following LGPL license applies to the replace
   7  *   ** library. This does NOT imply that all of Samba is released
   8  *   ** under the LGPL
   9  *
  10  * This library is free software; you can redistribute it and/or
  11  * modify it under the terms of the GNU Lesser General Public
  12  * License as published by the Free Software Foundation; either
  13  * version 3 of the License, or (at your option) any later version.
  14  *
  15  * This library is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  18  * Library General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU Lesser General Public
  21  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  22  */
  23
  24 #include "replace.h"
  25 #include <dirent.h>
  26 #include <unistd.h>
  27 #include <limits.h>
  28
  29 static int closefrom_sysconf(int lower)
  30 {
  31         long max_files, fd;
  32
  33         max_files = sysconf(_SC_OPEN_MAX);
  34         if (max_files == -1) {
  35                 max_files = 65536;
  36         }
  37
  38         for (fd=lower; fd<max_files; fd++) {
  39                 close(fd);
  40         }
  41
  42         return 0;
  43 }
  44
  45 static int closefrom_procfs(int lower)
  46 {
  47         DIR *dirp;
  48         int dir_fd;
  49         struct dirent *dp;
  50         int *fds = NULL;
  51         size_t num_fds = 0;
  52         size_t fd_array_size = 0;
  53         size_t i;
  54         int ret = ENOMEM;
  55
  56         dirp = opendir("/proc/self/fd");
  57         if (dirp == NULL) {
  58                 return errno;
  59         }
  60
  61         dir_fd = dirfd(dirp);
  62         if (dir_fd == -1) {
  63                 ret = errno;
  64                 goto fail;
  65         }
  66
  67         while ((dp = readdir(dirp)) != NULL) {
  68                 char *endptr;
  69                 unsigned long long fd;
  70
  71                 errno = 0;
  72
  73                 fd = strtoull(dp->d_name, &endptr, 10);
  74                 if ((fd == 0) && (errno == EINVAL)) {
  75                         continue;
  76                 }
  77                 if ((fd == ULLONG_MAX) && (errno == ERANGE)) {
  78                         continue;
  79                 }
  80                 if (*endptr != '\0') {
  81                         continue;
  82                 }
  83                 if (fd == dir_fd) {
  84                         continue;
  85                 }
  86                 if (fd > INT_MAX) {
  87                         continue;
  88                 }
  89                 if (fd < lower) {
  90                         continue;
  91                 }
  92
  93                 if (num_fds >= (fd_array_size / sizeof(int))) {
  94                         void *tmp;
  95
  96                         if (fd_array_size == 0) {
  97                                 fd_array_size = 16 * sizeof(int);
  98                         } else {
  99                                 if (fd_array_size + fd_array_size <
 100                                     fd_array_size) {
 101                                         /* overflow */
 102                                         goto fail;
 103                                 }
 104                                 fd_array_size = fd_array_size + fd_array_size;
 105                         }
 106
 107                         tmp = realloc(fds, fd_array_size);
 108                         if (tmp == NULL) {
 109                                 goto fail;
 110                         }
 111                         fds = tmp;
 112                 }
 113
 114                 fds[num_fds++] = fd;
 115         }
 116
 117         for (i=0; i<num_fds; i++) {
 118                 close(fds[i]);
 119         }
 120
 121         ret = 0;
 122 fail:
 123         closedir(dirp);
 124         free(fds);
 125         return ret;
 126 }
 127
 128 int rep_closefrom(int lower)
 129 {
 130         int ret;
 131
 132         ret = closefrom_procfs(lower);
 133         if (ret == 0) {
 134                 return 0;
 135         }
 136
 137         return closefrom_sysconf(lower);
 138 }