| 1 | /* Create /proc/self/fd-related names for subfiles of open directories.
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| 2 |
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| 3 | Copyright (C) 2006 Free Software Foundation, Inc.
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| 4 |
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| 5 | This program is free software; you can redistribute it and/or modify
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| 6 | it under the terms of the GNU General Public License as published by
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| 7 | the Free Software Foundation; either version 2, or (at your option)
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| 8 | any later version.
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| 9 |
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| 10 | This program is distributed in the hope that it will be useful,
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| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 13 | GNU General Public License for more details.
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| 14 |
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| 15 | You should have received a copy of the GNU General Public License
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| 16 | along with this program; if not, write to the Free Software Foundation,
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| 17 | Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
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| 18 |
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| 19 | /* Written by Paul Eggert. */
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| 20 |
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| 21 | #include <config.h>
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| 22 |
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| 23 | #include "openat-priv.h"
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| 24 |
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| 25 | #include <sys/types.h>
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| 26 | #include <sys/stat.h>
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| 27 | #include <fcntl.h>
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| 28 |
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| 29 | #include <stdio.h>
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| 30 | #include <string.h>
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| 31 |
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| 32 | #include "dirname.h"
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| 33 | #include "intprops.h"
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| 34 | #include "same-inode.h"
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| 35 | #include "xalloc.h"
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| 36 |
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| 37 | #define PROC_SELF_FD_FORMAT "/proc/self/fd/%d/%s"
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| 38 |
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| 39 | #define PROC_SELF_FD_NAME_SIZE_BOUND(len) \
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| 40 | (sizeof PROC_SELF_FD_FORMAT - sizeof "%d%s" \
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| 41 | + INT_STRLEN_BOUND (int) + (len) + 1)
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| 42 |
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| 43 |
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| 44 | /* Set BUF to the expansion of PROC_SELF_FD_FORMAT, using FD and FILE
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| 45 | respectively for %d and %s. If successful, return BUF if the
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| 46 | result fits in BUF, dynamically allocated memory otherwise. But
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| 47 | return NULL if /proc is not reliable. */
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| 48 | char *
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| 49 | openat_proc_name (char buf[OPENAT_BUFFER_SIZE], int fd, char const *file)
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| 50 | {
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| 51 | static int proc_status = 0;
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| 52 |
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| 53 | if (! proc_status)
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| 54 | {
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| 55 | /* Set PROC_STATUS to a positive value if /proc/self/fd is
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| 56 | reliable, and a negative value otherwise. Solaris 10
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| 57 | /proc/self/fd mishandles "..", and any file name might expand
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| 58 | to ".." after symbolic link expansion, so avoid /proc/self/fd
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| 59 | if it mishandles "..". Solaris 10 has openat, but this
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| 60 | problem is exhibited on code that built on Solaris 8 and
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| 61 | running on Solaris 10. */
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| 62 |
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| 63 | int proc_self_fd = open ("/proc/self/fd", O_RDONLY);
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| 64 | if (proc_self_fd < 0)
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| 65 | proc_status = -1;
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| 66 | else
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| 67 | {
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| 68 | struct stat proc_self_fd_dotdot_st;
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| 69 | struct stat proc_self_st;
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| 70 | char dotdot_buf[PROC_SELF_FD_NAME_SIZE_BOUND (sizeof ".." - 1)];
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| 71 | sprintf (dotdot_buf, PROC_SELF_FD_FORMAT, proc_self_fd, "..");
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| 72 | proc_status =
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| 73 | ((stat (dotdot_buf, &proc_self_fd_dotdot_st) == 0
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| 74 | && stat ("/proc/self", &proc_self_st) == 0
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| 75 | && SAME_INODE (proc_self_fd_dotdot_st, proc_self_st))
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| 76 | ? 1 : -1);
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| 77 | close (proc_self_fd);
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| 78 | }
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| 79 | }
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| 80 |
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| 81 | if (proc_status < 0)
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| 82 | return NULL;
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| 83 | else
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| 84 | {
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| 85 | size_t bufsize = PROC_SELF_FD_NAME_SIZE_BOUND (strlen (file));
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| 86 | char *result = (bufsize < OPENAT_BUFFER_SIZE ? buf : xmalloc (bufsize));
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| 87 | sprintf (result, PROC_SELF_FD_FORMAT, fd, file);
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| 88 | return result;
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| 89 | }
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| 90 | }
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