136 lines
4 KiB
C
136 lines
4 KiB
C
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/* Create /proc/self/fd-related names for subfiles of open directories.
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Copyright (C) 2006, 2009-2021 Free Software Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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/* Written by Paul Eggert. */
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#include <config.h>
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#include "openat-priv.h"
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#include <sys/types.h>
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#include <sys/stat.h>
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#include <fcntl.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#ifdef __KLIBC__
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# include <InnoTekLIBC/backend.h>
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#endif
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#include "intprops.h"
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/* Set BUF to the name of the subfile of the directory identified by
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FD, where the subfile is named FILE. If successful, return BUF if
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the result fits in BUF, dynamically allocated memory otherwise.
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Return NULL (setting errno) on error. */
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char *
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openat_proc_name (char buf[OPENAT_BUFFER_SIZE], int fd, char const *file)
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{
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char *result = buf;
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int dirlen;
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/* Make sure the caller gets ENOENT when appropriate. */
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if (!*file)
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{
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buf[0] = '\0';
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return buf;
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}
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#ifndef __KLIBC__
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# define PROC_SELF_FD_FORMAT "/proc/self/fd/%d/"
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{
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enum {
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PROC_SELF_FD_DIR_SIZE_BOUND
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= (sizeof PROC_SELF_FD_FORMAT - (sizeof "%d" - 1)
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+ INT_STRLEN_BOUND (int))
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};
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static int proc_status = 0;
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if (! proc_status)
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{
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/* Set PROC_STATUS to a positive value if /proc/self/fd is
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reliable, and a negative value otherwise. Solaris 10
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/proc/self/fd mishandles "..", and any file name might expand
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to ".." after symbolic link expansion, so avoid /proc/self/fd
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if it mishandles "..". Solaris 10 has openat, but this
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problem is exhibited on code that built on Solaris 8 and
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running on Solaris 10. */
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int proc_self_fd =
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open ("/proc/self/fd",
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O_SEARCH | O_DIRECTORY | O_NOCTTY | O_NONBLOCK | O_CLOEXEC);
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if (proc_self_fd < 0)
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proc_status = -1;
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else
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{
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/* Detect whether /proc/self/fd/%i/../fd exists, where %i is the
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number of a file descriptor open on /proc/self/fd. On Linux,
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that name resolves to /proc/self/fd, which was opened above.
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However, on Solaris, it may resolve to /proc/self/fd/fd, which
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cannot exist, since all names in /proc/self/fd are numeric. */
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char dotdot_buf[PROC_SELF_FD_DIR_SIZE_BOUND + sizeof "../fd" - 1];
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sprintf (dotdot_buf, PROC_SELF_FD_FORMAT "../fd", proc_self_fd);
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proc_status = access (dotdot_buf, F_OK) ? -1 : 1;
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close (proc_self_fd);
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}
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}
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if (proc_status < 0)
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return NULL;
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else
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{
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size_t bufsize = PROC_SELF_FD_DIR_SIZE_BOUND + strlen (file);
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if (OPENAT_BUFFER_SIZE < bufsize)
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{
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result = malloc (bufsize);
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if (! result)
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return NULL;
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}
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dirlen = sprintf (result, PROC_SELF_FD_FORMAT, fd);
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}
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}
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#else
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/* OS/2 kLIBC provides a function to retrieve a path from a fd. */
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{
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char dir[_MAX_PATH];
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size_t bufsize;
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if (__libc_Back_ioFHToPath (fd, dir, sizeof dir))
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return NULL;
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dirlen = strlen (dir);
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bufsize = dirlen + 1 + strlen (file) + 1; /* 1 for '/', 1 for null */
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if (OPENAT_BUFFER_SIZE < bufsize)
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{
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result = malloc (bufsize);
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if (! result)
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return NULL;
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}
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strcpy (result, dir);
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result[dirlen++] = '/';
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}
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#endif
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strcpy (result + dirlen, file);
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return result;
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}
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