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100 lines
3.1 KiB
C
100 lines
3.1 KiB
C
/* Close a range of file descriptors. Linux version.
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Copyright (C) 2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library 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 GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#include <arch-fd_to_filename.h>
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#include <dirent.h>
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#include <not-cancel.h>
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#include <stdbool.h>
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/* Fallback code: iterates over /proc/self/fd, closing each file descriptor
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that fall on the criteria. If DIRFD_FALLBACK is set, a failure on
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/proc/self/fd open will trigger a fallback that tries to close a file
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descriptor before proceed. */
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_Bool
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__closefrom_fallback (int from, _Bool dirfd_fallback)
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{
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bool ret = false;
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int dirfd = __open_nocancel (FD_TO_FILENAME_PREFIX, O_RDONLY | O_DIRECTORY,
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0);
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if (dirfd == -1)
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{
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/* The closefrom should work even when process can't open new files. */
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if (errno == ENOENT || !dirfd_fallback)
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goto err;
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for (int i = from; i < INT_MAX; i++)
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{
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int r = __close_nocancel (i);
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if (r == 0 || (r == -1 && errno != EBADF))
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break;
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}
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dirfd = __open_nocancel (FD_TO_FILENAME_PREFIX, O_RDONLY | O_DIRECTORY,
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0);
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if (dirfd == -1)
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return false;
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}
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char buffer[1024];
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while (true)
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{
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ssize_t ret = __getdents64 (dirfd, buffer, sizeof (buffer));
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if (ret == -1)
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goto err;
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else if (ret == 0)
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break;
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/* If any file descriptor is closed it resets the /proc/self position
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read again from the start (to obtain any possible kernel update). */
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bool closed = false;
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char *begin = buffer, *end = buffer + ret;
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while (begin != end)
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{
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unsigned short int d_reclen;
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memcpy (&d_reclen, begin + offsetof (struct dirent64, d_reclen),
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sizeof (d_reclen));
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const char *dname = begin + offsetof (struct dirent64, d_name);
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begin += d_reclen;
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if (dname[0] == '.')
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continue;
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int fd = 0;
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for (const char *s = dname; (unsigned int) (*s) - '0' < 10; s++)
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fd = 10 * fd + (*s - '0');
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if (fd == dirfd || fd < from)
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continue;
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/* We ignore close errors because EBADF, EINTR, and EIO means the
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descriptor has been released. */
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__close_nocancel (fd);
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closed = true;
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}
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if (closed && __lseek (dirfd, 0, SEEK_SET) < 0)
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goto err;
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}
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ret = true;
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err:
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__close_nocancel (dirfd);
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return ret;
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}
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