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/* Work around unlinkat bugs on Solaris 9 and Hurd.
Copyright (C) 2009-2024 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>. */
/* Written by Eric Blake. */
#include <config.h>
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <string.h>
#include <sys/stat.h>
#include <stdlib.h>
#include "filename.h"
#include "openat.h"
#if HAVE_UNLINKAT
# undef unlinkat
/* unlinkat without AT_REMOVEDIR does not honor trailing / on Solaris 9.
Hurd has the same issue.
unlinkat without AT_REMOVEDIR erroneously ignores ".." on Darwin 14.
Solve these in a similar manner to unlink. */
int
rpl_unlinkat (int fd, char const *name, int flag)
{
size_t len;
int result = 0;
/* rmdir behavior has no problems with trailing slash. */
if (flag & AT_REMOVEDIR)
return unlinkat (fd, name, flag);
len = strlen (name);
if (len && ISSLASH (name[len - 1]))
{
/* See the lengthy comment in unlink.c why we disobey the POSIX
rule of letting unlink("link-to-dir/") attempt to unlink a
directory. */
struct stat st;
result = fstatat (fd, name, &st, AT_SYMLINK_NOFOLLOW);
if (result == 0 || errno == EOVERFLOW)
{
/* Trailing NUL will overwrite the trailing slash. */
char *short_name = malloc (len);
if (!short_name)
{
errno = EPERM;
return -1;
}
memcpy (short_name, name, len);
while (len && ISSLASH (short_name[len - 1]))
short_name[--len] = '\0';
if (len && (fstatat (fd, short_name, &st, AT_SYMLINK_NOFOLLOW)
|| S_ISLNK (st.st_mode)))
{
free (short_name);
errno = EPERM;
return -1;
}
free (short_name);
result = 0;
}
}
if (!result)
{
# if UNLINK_PARENT_BUG
if (len >= 2 && name[len - 1] == '.' && name[len - 2] == '.'
&& (len == 2 || ISSLASH (name[len - 3])))
{
errno = EISDIR; /* could also use EPERM */
return -1;
}
# endif
result = unlinkat (fd, name, flag);
}
return result;
}
#else /* !HAVE_UNLINKAT */
/* Replacement for Solaris' function by the same name.
<https://www.google.com/search?q=unlinkat+site:docs.oracle.com>
First, try to simulate it via (unlink|rmdir) ("/proc/self/fd/FD/FILE").
Failing that, simulate it via save_cwd/fchdir/(unlink|rmdir)/restore_cwd.
If either the save_cwd or the restore_cwd fails (relatively unlikely),
then give a diagnostic and exit nonzero.
Otherwise, this function works just like Solaris' unlinkat. */
# define AT_FUNC_NAME unlinkat
# define AT_FUNC_F1 rmdir
# define AT_FUNC_F2 unlink
# define AT_FUNC_USE_F1_COND AT_REMOVEDIR
# define AT_FUNC_POST_FILE_PARAM_DECLS , int flag
# define AT_FUNC_POST_FILE_ARGS /* empty */
# include "at-func.c"
# undef AT_FUNC_NAME
# undef AT_FUNC_F1
# undef AT_FUNC_F2
# undef AT_FUNC_USE_F1_COND
# undef AT_FUNC_POST_FILE_PARAM_DECLS
# undef AT_FUNC_POST_FILE_ARGS
#endif /* !HAVE_UNLINKAT */
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