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

[Ken Brown <kbrown@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=8889d21010b751868dfa6178b1cacbf375454dfe

commit 8889d21010b751868dfa6178b1cacbf375454dfe
Author: Ken Brown <kbrown@cornell.edu>
Date:   Mon Feb 22 09:21:00 2021 -0500

    Cygwin: fix fstatvfs on sockets that are not socket files
    
    If fstatvfs(2) is called on an AF_LOCAL or AF_UNIX socket that is not
    a socket file, the current code calls fhandler_disk_file::fstatvfs 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::fstatvfs only if the
    fhandler_socket object is a socket file (determined by testing
    dev().isfs()).

Diff:
---
 winsup/cygwin/fhandler_socket_local.cc |  5 ++++-
 winsup/cygwin/fhandler_socket_unix.cc  | 14 +++++++++++---
 2 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/winsup/cygwin/fhandler_socket_local.cc b/winsup/cygwin/fhandler_socket_local.cc
index f8adf6c46..5ca6d8550 100644
--- a/winsup/cygwin/fhandler_socket_local.cc
+++ b/winsup/cygwin/fhandler_socket_local.cc
@@ -690,8 +690,11 @@ fhandler_socket_local::fstat (struct stat *buf)
 int __reg2
 fhandler_socket_local::fstatvfs (struct statvfs *sfs)
 {
-  if (get_sun_path () && get_sun_path ()[0] == '\0')
+  if (!dev ().isfs ())
+    /* fstatvfs called on a socket. */
     return fhandler_socket_wsock::fstatvfs (sfs);
+
+  /* statvfs on a socket file or fstatvfs on a socket opened w/ O_PATH. */
   if (get_flags () & O_PATH)
     /* We already have a handle. */
     {
diff --git a/winsup/cygwin/fhandler_socket_unix.cc b/winsup/cygwin/fhandler_socket_unix.cc
index 8091fa820..06db929ed 100644
--- a/winsup/cygwin/fhandler_socket_unix.cc
+++ b/winsup/cygwin/fhandler_socket_unix.cc
@@ -2354,10 +2354,18 @@ fhandler_socket_unix::fstat (struct stat *buf)
 int __reg2
 fhandler_socket_unix::fstatvfs (struct statvfs *sfs)
 {
-  if (sun_path ()
-      && (sun_path ()->un_len <= (socklen_t) sizeof (sa_family_t)
-	  || sun_path ()->un.sun_path[0] == '\0'))
+  if (!dev ().isfs ())
+    /* fstatvfs called on a socket. */
     return fhandler_socket::fstatvfs (sfs);
+
+  /* statvfs on a socket file or fstatvfs on a socket opened w/ O_PATH. */
+  if (get_flags () & O_PATH)
+    /* We already have a handle. */
+    {
+      HANDLE h = get_handle ();
+      if (h)
+	return fstatvfs_by_handle (h, sfs);
+    }
   fhandler_disk_file fh (pc);
   fh.get_device () = FH_FS;
   return fh.fstatvfs (sfs);