valido, e doveva essere passato sempre con valore nullo.} che richiede di
dereferenziare i collegamenti simbolici. Inoltre a partire dal kernel 3.11 si
può usare \const{AT\_EMPTY\_PATH} per creare un nuovo \textit{hard link} al
-file associato al file descriptor \param{olddirfd} (ottenuto ad esempio usando
-\func{open} con \const{O\_PATH}) che però in questo caso non può essere una
-directory.
+file associato al file descriptor \param{olddirfd}.
+
% NOTE per la discussione sui problemi di sicurezza relativi a questa
% funzionalità vedi http://lwn.net/Articles/562488/
-La funzione però prevede un comportamento specifico nel caso che
+La funzione prevede inoltre un comportamento specifico nel caso che
\param{olddirfd} faccia riferimento ad un file anonimo ottenuto usando
\func{open} con \const{O\_TMPFILE}. In generale quando il file associato ad
-\param{olddirfd} ha un numero di link nullo, la funzione fallisce, c'è però
-una
+\param{olddirfd} ha un numero di link nullo (come in questo caso), la funzione
+fallisce, c'è però una
l'uso di \const{AT\_EMPTY\_PATH} assume un significato
--- /dev/null
+/* test_linkat.c
+ *
+ * Copyright (C) 2019 Simone Piccardi
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or (at
+ * your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ */
+/****************************************************************
+ *
+ * Program test_linkat.c:
+ * Program to test use of linkat and O_TMPFILE and other combinations
+ *
+ * Author: Simone Piccardi
+ * Oct. 2018
+ *
+ * Usage: testlinkat -h give all info's
+ *
+ ****************************************************************/
+/*
+ * Include needed headers
+ */
+#define _GNU_SOURCE
+#include <errno.h> /* error definitions and routines */
+#include <stdlib.h> /* C standard library */
+#include <unistd.h> /* unix standard library */
+#include <stdio.h> /* standard I/O library */
+#include <string.h> /* C strings library */
+#include <limits.h>
+#include <libgen.h> /* needed for dirname e basename */
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <fcntl.h>
+
+/* Help printing routine */
+void usage(void);
+
+int main(int argc, char *argv[])
+{
+/*
+ * Variables definition
+ */
+ int i;
+ int wait=0;
+ char *srcfile = NULL;
+ /*
+ * Input section: decode command line parameters
+ * Use getopt function
+ */
+ opterr = 0; /* don't want writing to stderr */
+ while ( (i = getopt(argc, argv, "hw:f:")) != -1) {
+ switch (i) {
+ /*
+ * Handling options
+ */
+ case 'h': /* help option */
+ printf("Wrong -h option use\n");
+ usage();
+ return -1;
+ break;
+ case 'w': /* time to wait in s */
+ wait = strtol(optarg, NULL, 10); /* convert input */
+ break;
+ case 'f': /* using a source file */
+ srcfile = optarg;
+ break;
+ case '?': /* unrecognized options */
+ printf("Unrecognized options -%c\n",optopt);
+ usage();
+ default: /* should not reached */
+ usage();
+ }
+ }
+ /* ***********************************************************
+ *
+ * Options processing completed
+ *
+ * Main code beginning
+ *
+ * ***********************************************************/
+ /* There must be 1 remaing parameters */
+ if ( (argc-optind) != 1 ) {
+ printf("From %d arguments, removed %d options\n", argc, optind);
+ usage();
+ }
+ char *path, *dir, *file;
+ char pattern[] = "prova prova prova\n";
+ path = strdup(argv[optind]);
+ file = basename(argv[optind]);
+ dir = dirname(argv[optind]);
+ printf("Working on dir %s file: %s\nwith path: %s\n",
+ dir, file, path);
+ int fd, newfd;
+ if ( ! srcfile ) {
+ fd = open(dir, O_TMPFILE|O_RDWR,S_IRUSR|S_IWUSR);
+ if ( fd <= 0 )
+ perror("cannot open TMPFILE");
+ if ( (i = write(fd, pattern, sizeof(pattern))) < 0 )
+ perror("cannot write on TMPFILE");
+ else
+ printf("saved %d chars on fd %d\n", i, fd);
+ } else {
+ printf("source is %s\n", srcfile);
+ if ( (fd = open(srcfile, O_RDONLY)) < 0 ) {
+ perror("cannot open source");
+ exit(1);
+ }
+ }
+ newfd = open(dir, O_PATH|O_RDWR);
+ int err;
+ err = linkat(fd, "", newfd, file, AT_EMPTY_PATH);
+ if ( err < 0 ) {
+ perror("error on creating TMPFILE");
+ printf("cannot link fd %d on fd %d, %s with AT_EMPTY_PATH\n",
+ fd, newfd, file);
+ char fdpath[PATH_MAX];
+ snprintf(fdpath, PATH_MAX, "/proc/self/fd/%d", fd);
+ printf("fd path %s\n", fdpath);
+ err = linkat(AT_FDCWD, fdpath, newfd, file, AT_SYMLINK_FOLLOW);
+ if ( err < 0 ) {
+ perror("still error creating TMPFILE");
+ sleep(wait);
+ exit(1);
+ }
+ if ( fchmodat(newfd, file,S_IRUSR|S_IWUSR,0) < 0 )
+ perror("Cannot change permission to new file");
+ }
+ free(path);
+ return 0;
+}
+/*
+ * routine to print usage info and exit
+ */
+void usage(void) {
+ printf("Program testlinkat : test fopen for a file \n");
+ printf("Usage:\n");
+ printf(" testfopen [-h] file mode \n");
+ printf(" -h print this help\n");
+
+ exit(1);
+}
+
projects / gapil.git / commitdiff