| 1 | /* Create /proc/self/fd-related names for subfiles of open directories.
|
|---|
| 2 |
|
|---|
| 3 | Copyright (C) 2006, 2009-2012 Free Software Foundation, Inc.
|
|---|
| 4 |
|
|---|
| 5 | This program is free software: you can redistribute it and/or modify
|
|---|
| 6 | it under the terms of the GNU General Public License as published by
|
|---|
| 7 | the Free Software Foundation; either version 3 of the License, or
|
|---|
| 8 | (at your option) any later version.
|
|---|
| 9 |
|
|---|
| 10 | This program is distributed in the hope that it will be useful,
|
|---|
| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|---|
| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|---|
| 13 | GNU General Public License for more details.
|
|---|
| 14 |
|
|---|
| 15 | You should have received a copy of the GNU General Public License
|
|---|
| 16 | along with this program. If not, see <http://www.gnu.org/licenses/>. */
|
|---|
| 17 |
|
|---|
| 18 | /* Written by Paul Eggert. */
|
|---|
| 19 |
|
|---|
| 20 | #include <config.h>
|
|---|
| 21 |
|
|---|
| 22 | #include "openat-priv.h"
|
|---|
| 23 |
|
|---|
| 24 | #include <sys/types.h>
|
|---|
| 25 | #include <sys/stat.h>
|
|---|
| 26 | #include <fcntl.h>
|
|---|
| 27 |
|
|---|
| 28 | #include <stdio.h>
|
|---|
| 29 | #include <stdlib.h>
|
|---|
| 30 | #include <string.h>
|
|---|
| 31 | #include <unistd.h>
|
|---|
| 32 |
|
|---|
| 33 | #include "intprops.h"
|
|---|
| 34 |
|
|---|
| 35 | /* The results of open() in this file are not used with fchdir,
|
|---|
| 36 | and we do not leak fds to any single-threaded code that could use stdio,
|
|---|
| 37 | therefore save some unnecessary work in fchdir.c.
|
|---|
| 38 | FIXME - if the kernel ever adds support for multi-thread safety for
|
|---|
| 39 | avoiding standard fds, then we should use open_safer. */
|
|---|
| 40 | #undef open
|
|---|
| 41 | #undef close
|
|---|
| 42 |
|
|---|
| 43 | #define PROC_SELF_FD_FORMAT "/proc/self/fd/%d/%s"
|
|---|
| 44 |
|
|---|
| 45 | #define PROC_SELF_FD_NAME_SIZE_BOUND(len) \
|
|---|
| 46 | (sizeof PROC_SELF_FD_FORMAT - sizeof "%d%s" \
|
|---|
| 47 | + INT_STRLEN_BOUND (int) + (len) + 1)
|
|---|
| 48 |
|
|---|
| 49 |
|
|---|
| 50 | /* Set BUF to the expansion of PROC_SELF_FD_FORMAT, using FD and FILE
|
|---|
| 51 | respectively for %d and %s. If successful, return BUF if the
|
|---|
| 52 | result fits in BUF, dynamically allocated memory otherwise. But
|
|---|
| 53 | return NULL if /proc is not reliable, either because the operating
|
|---|
| 54 | system support is lacking or because memory is low. */
|
|---|
| 55 | char *
|
|---|
| 56 | openat_proc_name (char buf[OPENAT_BUFFER_SIZE], int fd, char const *file)
|
|---|
| 57 | {
|
|---|
| 58 | static int proc_status = 0;
|
|---|
| 59 |
|
|---|
| 60 | /* Make sure the caller gets ENOENT when appropriate. */
|
|---|
| 61 | if (!*file)
|
|---|
| 62 | {
|
|---|
| 63 | buf[0] = '\0';
|
|---|
| 64 | return buf;
|
|---|
| 65 | }
|
|---|
| 66 |
|
|---|
| 67 | if (! proc_status)
|
|---|
| 68 | {
|
|---|
| 69 | /* Set PROC_STATUS to a positive value if /proc/self/fd is
|
|---|
| 70 | reliable, and a negative value otherwise. Solaris 10
|
|---|
| 71 | /proc/self/fd mishandles "..", and any file name might expand
|
|---|
| 72 | to ".." after symbolic link expansion, so avoid /proc/self/fd
|
|---|
| 73 | if it mishandles "..". Solaris 10 has openat, but this
|
|---|
| 74 | problem is exhibited on code that built on Solaris 8 and
|
|---|
| 75 | running on Solaris 10. */
|
|---|
| 76 |
|
|---|
| 77 | int proc_self_fd = open ("/proc/self/fd",
|
|---|
| 78 | O_SEARCH | O_DIRECTORY | O_NOCTTY | O_NONBLOCK);
|
|---|
| 79 | if (proc_self_fd < 0)
|
|---|
| 80 | proc_status = -1;
|
|---|
| 81 | else
|
|---|
| 82 | {
|
|---|
| 83 | /* Detect whether /proc/self/fd/%i/../fd exists, where %i is the
|
|---|
| 84 | number of a file descriptor open on /proc/self/fd. On Linux,
|
|---|
| 85 | that name resolves to /proc/self/fd, which was opened above.
|
|---|
| 86 | However, on Solaris, it may resolve to /proc/self/fd/fd, which
|
|---|
| 87 | cannot exist, since all names in /proc/self/fd are numeric. */
|
|---|
| 88 | char dotdot_buf[PROC_SELF_FD_NAME_SIZE_BOUND (sizeof "../fd" - 1)];
|
|---|
| 89 | sprintf (dotdot_buf, PROC_SELF_FD_FORMAT, proc_self_fd, "../fd");
|
|---|
| 90 | proc_status = access (dotdot_buf, F_OK) ? -1 : 1;
|
|---|
| 91 | close (proc_self_fd);
|
|---|
| 92 | }
|
|---|
| 93 | }
|
|---|
| 94 |
|
|---|
| 95 | if (proc_status < 0)
|
|---|
| 96 | return NULL;
|
|---|
| 97 | else
|
|---|
| 98 | {
|
|---|
| 99 | size_t bufsize = PROC_SELF_FD_NAME_SIZE_BOUND (strlen (file));
|
|---|
| 100 | char *result = buf;
|
|---|
| 101 | if (OPENAT_BUFFER_SIZE < bufsize)
|
|---|
| 102 | {
|
|---|
| 103 | result = malloc (bufsize);
|
|---|
| 104 | if (! result)
|
|---|
| 105 | return NULL;
|
|---|
| 106 | }
|
|---|
| 107 | sprintf (result, PROC_SELF_FD_FORMAT, fd, file);
|
|---|
| 108 | return result;
|
|---|
| 109 | }
|
|---|
| 110 | }
|
|---|