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Cygwin: fstatat, fchownat: support the AT_EMPTY_PATH flag

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Following Linux, allow the pathname argument to be an empty string if
the AT_EMPTY_PATH flag is specified.  In this case the dirfd argument
can refer to any type of file, not just a directory, and the call
operates on that file.  In particular, dirfd can refer to a symlink
that was opened with O_PATH | O_NOFOLLOW.
This commit is contained in:
Ken Brown
2019-12-27 17:38:32 -05:00
parent 6cc05784e1
commit 352dbd304b
1 changed files with 41 additions and 6 deletions
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47
winsup/cygwin/syscalls.cc
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@@ -4785,14 +4785,36 @@ fchownat (int dirfd, const char *pathname, uid_t uid, gid_t gid, int flags)
tmp_pathbuf tp;
__try
{
if (flags & ~AT_SYMLINK_NOFOLLOW)
if (flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH))
{
set_errno (EINVAL);
__leave;
}
char *path = tp.c_get ();
if (gen_full_path_at (path, dirfd, pathname))
__leave;
int res = gen_full_path_at (path, dirfd, pathname);
if (res)
{
if (!(errno == ENOENT && (flags & AT_EMPTY_PATH)))
__leave;
/* pathname is an empty string. Operate on dirfd. */
if (dirfd == AT_FDCWD)
{
cwdstuff::cwd_lock.acquire ();
strcpy (path, cygheap->cwd.get_posix ());
cwdstuff::cwd_lock.release ();
}
else
{
cygheap_fdget cfd (dirfd);
if (cfd < 0)
__leave;
strcpy (path, cfd->get_name ());
/* If dirfd refers to a symlink (which was necessarily
opened with O_PATH | O_NOFOLLOW), we must operate
directly on that symlink.. */
flags = AT_SYMLINK_NOFOLLOW;
}
}
return chown_worker (path, (flags & AT_SYMLINK_NOFOLLOW)
? PC_SYM_NOFOLLOW : PC_SYM_FOLLOW, uid, gid);
}
@@ -4808,14 +4830,27 @@ fstatat (int dirfd, const char *__restrict pathname, struct stat *__restrict st,
tmp_pathbuf tp;
__try
{
if (flags & ~AT_SYMLINK_NOFOLLOW)
if (flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH))
{
set_errno (EINVAL);
__leave;
}
char *path = tp.c_get ();
if (gen_full_path_at (path, dirfd, pathname))
__leave;
int res = gen_full_path_at (path, dirfd, pathname);
if (res)
{
if (!(errno == ENOENT && (flags & AT_EMPTY_PATH)))
__leave;
/* pathname is an empty string. Operate on dirfd. */
if (dirfd == AT_FDCWD)
{
cwdstuff::cwd_lock.acquire ();
strcpy (path, cygheap->cwd.get_posix ());
cwdstuff::cwd_lock.release ();
}
else
return fstat (dirfd, st);
}
path_conv pc (path, ((flags & AT_SYMLINK_NOFOLLOW)
? PC_SYM_NOFOLLOW : PC_SYM_FOLLOW)
| PC_POSIX | PC_KEEP_HANDLE, stat_suffixes);