Re: [PATCH] Cygwin: pipe: Give up to use query_hdl for non-cygwin apps.

[Takashi Yano <takashi.yano@nifty.ne.jp>]

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On Tue, 5 Mar 2024 11:14:46 +0100
Corinna Vinschen wrote:
> On Mar  5 09:06, Takashi Yano wrote:
> > On Mon, 4 Mar 2024 18:38:07 +0100
> > Corinna Vinschen wrote:
> > > On Mar  4 16:45, ASSI wrote:
> > > > Corinna Vinschen writes:
> > > > > Right you are.  We always said that independent Cygwin installations
> > > > > are supposed to *stay* independent.
> > > > >
> > > > > Keep in mind that they don't share the same shared objects in the native
> > > > > NT namespace and they don't know of each other.  It's not only the
> > > > > process table but also in-use FIFO stuff, pty info, etc.
> > > > 
> > > > What I was getting at is that a process not showing up in the process
> > > > list in one Cygwin installation doesn't automatically mean it's a native
> > > > Windows process, it could be a process started by an independent Cygwin
> > > > installation.  So this way of checking for "native" Windows processes
> > > > may or may not do what was originally intended.
> > > 
> > > But that was my point. A "foreign" Cygwin process from another
> > > installation is not a Cygwin process.  Lots of interoperability
> > > just won't work, so it's basically a native process.
> > 
> > Actually, I think query_hdl can be retrieved from the process
> > from another installation of cygwin using NtQueryInformationProcess()
> > with ProcessHandleInformation. However, I cannot imagne the case
> > that the pipe is made by one cygwin installation but the reader
> > process is from another installation of cygwin.
> > 
> > BTW, what about v2 patch itself?
> 
> It does the job with less code and less memory, which is good.
> I would change the comment
> 
>   stop to try to get query_hdl for non-cygwin apps
> 
> to something like
> 
>   don't try to fetch query_hdl from non-cygwin apps
> 
> "stop trying" is a bit of a back-reference to the old code, which
> is not necessary, I think.

I'll submit v3 patch. Please review.

> This doesn't affect your patch, but while looking into this, what
> strikes me as weird is that fhandler_pipe::temporary_query_hdl() calls
> NtQueryObject() and assembles the pipe name via swscanf() every time it
> is called.
> 
> Wouldn't it make sense to store the name in the fhandler's
> path_conv::wide_path/uni_path at creation time instead?
> The wide_path member is not used at all in pipes, ostensibly.

Is the patch attached as you intended?

-- 
Takashi Yano <takashi.yano@nifty.ne.jp>

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From 998027fe7a7a56af9507341266c9fcadee66beb9 Mon Sep 17 00:00:00 2001
From: Takashi Yano <takashi.yano@nifty.ne.jp>
Date: Tue, 5 Mar 2024 23:34:21 +0900
Subject: [PATCH] Cygwin: pipe: Simplify chhecking procedure of query_hdl.

This patch eliminates verbose NtQueryObject() calls in the procedure
to get query_hdl by storing pipe name into fhandler_base::pc when
the pipe is created.  fhandler_pipe::temporary_query_hdl() uses the
storedpipe name rather than the name retrieved by NtQueryObject().

Suggested-by: Corinna Vinschen <corinna@vinschen.de>
Signed-off-by: Takashi Yano <takashi.yano@nifty.ne.jp>
---
 winsup/cygwin/fhandler/pipe.cc          | 39 ++++++++++++-------------
 winsup/cygwin/local_includes/fhandler.h |  3 --
 2 files changed, 19 insertions(+), 23 deletions(-)

diff --git a/winsup/cygwin/fhandler/pipe.cc b/winsup/cygwin/fhandler/pipe.cc
index c877d89d7..0611dd1c3 100644
--- a/winsup/cygwin/fhandler/pipe.cc
+++ b/winsup/cygwin/fhandler/pipe.cc
@@ -93,6 +93,19 @@ fhandler_pipe::init (HANDLE f, DWORD a, mode_t mode, int64_t uniq_id)
        even with FILE_SYNCHRONOUS_IO_NONALERT. */
     set_pipe_non_blocking (get_device () == FH_PIPER ?
 			   true : is_nonblocking ());
+
+  /* Store pipe name to path_conv pc for query_hdl check */
+  if (get_dev () == FH_PIPEW)
+    {
+      ULONG len;
+      tmp_pathbuf tp;
+      OBJECT_NAME_INFORMATION *ntfn = (OBJECT_NAME_INFORMATION *) tp.w_get ();
+      NTSTATUS status = NtQueryObject (f, ObjectNameInformation, ntfn,
+				       65536, &len);
+      if (NT_SUCCESS (status) && ntfn->Name.Buffer)
+	pc.set_nt_native_path (&ntfn->Name);
+    }
+
   return 1;
 }
 
@@ -1149,6 +1162,9 @@ fhandler_pipe::temporary_query_hdl ()
   tmp_pathbuf tp;
   OBJECT_NAME_INFORMATION *ntfn = (OBJECT_NAME_INFORMATION *) tp.w_get ();
 
+  UNICODE_STRING *name = pc.get_nt_native_path (NULL);
+  name->Buffer[name->Length / sizeof (WCHAR)] = L'\0';
+
   /* Try process handle opened and pipe handle value cached first
      in order to reduce overhead. */
   if (query_hdl_proc && query_hdl_value)
@@ -1161,14 +1177,7 @@ fhandler_pipe::temporary_query_hdl ()
       status = NtQueryObject (h, ObjectNameInformation, ntfn, 65536, &len);
       if (!NT_SUCCESS (status) || !ntfn->Name.Buffer)
 	goto hdl_err;
-      ntfn->Name.Buffer[ntfn->Name.Length / sizeof (WCHAR)] = L'\0';
-      uint64_t key;
-      DWORD pid;
-      LONG id;
-      if (swscanf (ntfn->Name.Buffer,
-		   L"\\Device\\NamedPipe\\%llx-%u-pipe-nt-0x%x",
-		   &key, &pid, &id) == 3 &&
-	  key == pipename_key && pid == pipename_pid && id == pipename_id)
+      if (RtlEqualUnicodeString (name, &ntfn->Name, FALSE))
 	return h;
 hdl_err:
       CloseHandle (h);
@@ -1178,19 +1187,9 @@ cache_err:
       query_hdl_value = NULL;
     }
 
-  status = NtQueryObject (get_handle (), ObjectNameInformation, ntfn,
-			  65536, &len);
-  if (!NT_SUCCESS (status) || !ntfn->Name.Buffer)
+  if (name->Length == 0 || name->Buffer == NULL)
     return NULL; /* Non cygwin pipe? */
-  WCHAR name[MAX_PATH];
-  int namelen = min (ntfn->Name.Length / sizeof (WCHAR), MAX_PATH-1);
-  memcpy (name, ntfn->Name.Buffer, namelen * sizeof (WCHAR));
-  name[namelen] = L'\0';
-  if (swscanf (name, L"\\Device\\NamedPipe\\%llx-%u-pipe-nt-0x%x",
-	       &pipename_key, &pipename_pid, &pipename_id) != 3)
-    return NULL; /* Non cygwin pipe? */
-
-  return get_query_hdl_per_process (name, ntfn); /* Since Win8 */
+  return get_query_hdl_per_process (name->Buffer, ntfn); /* Since Win8 */
 }
 
 HANDLE
diff --git a/winsup/cygwin/local_includes/fhandler.h b/winsup/cygwin/local_includes/fhandler.h
index 6ddf37370..028eb49d0 100644
--- a/winsup/cygwin/local_includes/fhandler.h
+++ b/winsup/cygwin/local_includes/fhandler.h
@@ -1216,9 +1216,6 @@ private:
   HANDLE query_hdl_proc;
   HANDLE query_hdl_value;
   HANDLE query_hdl_close_req_evt;
-  uint64_t pipename_key;
-  DWORD pipename_pid;
-  LONG pipename_id;
   void release_select_sem (const char *);
   HANDLE get_query_hdl_per_process (WCHAR *, OBJECT_NAME_INFORMATION *);
 public:
-- 
2.43.0