[newlib-cygwin] Cygwin: fix facl on sockets that are not socket files

[Ken Brown <kbrown@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=012427c96eccd195b60cd61f3817f550f6563275

commit 012427c96eccd195b60cd61f3817f550f6563275
Author: Ken Brown <kbrown@cornell.edu>
Date:   Mon Feb 22 10:13:09 2021 -0500

    Cygwin: fix facl on sockets that are not socket files
    
    If facl(2) is called on an AF_LOCAL or AF_UNIX socket that is not a
    socket file, the current code calls fhandler_disk_file::facl in most
    cases.  The latter expects to be operating on a disk file and uses the
    socket's io_handle, which is not a file handle.
    
    Fix this by calling fhandler_disk_file::facl only if the
    fhandler_socket object is a file (determined by testing dev().isfs()).

Diff:
---
 winsup/cygwin/fhandler_socket_local.cc | 6 +++++-
 winsup/cygwin/fhandler_socket_unix.cc  | 8 +++++---
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/winsup/cygwin/fhandler_socket_local.cc b/winsup/cygwin/fhandler_socket_local.cc
index 349ade897..22586c0dd 100644
--- a/winsup/cygwin/fhandler_socket_local.cc
+++ b/winsup/cygwin/fhandler_socket_local.cc
@@ -737,8 +737,12 @@ fhandler_socket_local::fchown (uid_t uid, gid_t gid)
 int
 fhandler_socket_local::facl (int cmd, int nentries, aclent_t *aclbufp)
 {
-  if (get_sun_path () && get_sun_path ()[0] == '\0')
+  if (!dev ().isfs ())
+    /* facl called on a socket. */
     return fhandler_socket_wsock::facl (cmd, nentries, aclbufp);
+
+  /* facl on a socket file.  [We won't get here if facl is called on a
+     socket opened w/ O_PATH.] */
   fhandler_disk_file fh (pc);
   return fh.facl (cmd, nentries, aclbufp);
 }
diff --git a/winsup/cygwin/fhandler_socket_unix.cc b/winsup/cygwin/fhandler_socket_unix.cc
index 573864b9f..fae07367d 100644
--- a/winsup/cygwin/fhandler_socket_unix.cc
+++ b/winsup/cygwin/fhandler_socket_unix.cc
@@ -2408,10 +2408,12 @@ fhandler_socket_unix::fchown (uid_t uid, gid_t gid)
 int
 fhandler_socket_unix::facl (int cmd, int nentries, aclent_t *aclbufp)
 {
-  if (sun_path ()
-      && (sun_path ()->un_len <= (socklen_t) sizeof (sa_family_t)
-	  || sun_path ()->un.sun_path[0] == '\0'))
+  if (!dev ().isfs ())
+    /* facl called on a socket. */
     return fhandler_socket::facl (cmd, nentries, aclbufp);
+
+  /* facl on a socket file.  [We won't get here if facl is called on a
+     socket opened w/ O_PATH.] */
   fhandler_disk_file fh (pc);
   return fh.facl (cmd, nentries, aclbufp);
 }