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