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* [newlib-cygwin] Cygwin: fstatat, fchownat: support the AT_EMPTY_PATH flag
@ 2020-01-20 14:49 Ken Brown
0 siblings, 0 replies; only message in thread
From: Ken Brown @ 2020-01-20 14:49 UTC (permalink / raw)
To: cygwin-cvs
https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=352dbd304be48cd47de4f588031b98b8e0202f33
commit 352dbd304be48cd47de4f588031b98b8e0202f33
Author: Ken Brown <kbrown@cornell.edu>
Date: Fri Dec 27 17:38:32 2019 -0500
Cygwin: fstatat, fchownat: support the AT_EMPTY_PATH flag
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.
Diff:
---
winsup/cygwin/syscalls.cc | 47 +++++++++++++++++++++++++++++++++++++++++------
1 file changed, 41 insertions(+), 6 deletions(-)
diff --git a/winsup/cygwin/syscalls.cc b/winsup/cygwin/syscalls.cc
index 282d9e0..4956b6f 100644
--- a/winsup/cygwin/syscalls.cc
+++ b/winsup/cygwin/syscalls.cc
@@ -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);
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