[newlib-cygwin/cygwin-3_3-branch] Cygwin: make sure exec'ed process exists early in process list

[newlib-cygwin/cygwin-3_3-branch] Cygwin: make sure exec'ed process exists early in process list

[Corinna Vinschen]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=a8629d6eaf4695d353b73f9d88aa123fedc2827a

commit a8629d6eaf4695d353b73f9d88aa123fedc2827a
Author: Corinna Vinschen <corinna@vinschen.de>
Date:   Thu May 19 10:46:33 2022 +0200

    Cygwin: make sure exec'ed process exists early in process list
    
    killpg(pgid, 0) (or kill_pgrp(pgid, si_signo=0), in signal.cc)
    fails (returns -1) even when there is a process in the process
    group pgid, if the process is in the middle of spawnve(), see
    
      https://cygwin.com/pipermail/cygwin/2022-May/251479.html
    
    When exec'ing a process the assumption is that the exec'ed process creates its
    own symlink (in pinfo::thisproc() in pinfo.cc). If the exec'ing process
    calls NtClose on it's own winpid symlink, but the exec'ed process didn't
    progress enough into initialization, there's a slim chance that neither
    the exec'ing process, nor the exec'ed process has a winpid symlink
    attached.
    
    Always create the winpid symlink in spawn.cc, even for exec'ed Cygwin
    processes.  Make sure to dup the handle into the new process, and stop
    creating the winpid symlink in exec'ed processes.
    
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 winsup/cygwin/pinfo.cc      |  6 ++++--
 winsup/cygwin/release/3.3.6 |  4 ++++
 winsup/cygwin/spawn.cc      | 15 ++++++++-------
 3 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/winsup/cygwin/pinfo.cc b/winsup/cygwin/pinfo.cc
index 5e04ea3da..a16e2198a 100644
--- a/winsup/cygwin/pinfo.cc
+++ b/winsup/cygwin/pinfo.cc
@@ -55,10 +55,11 @@ void
 pinfo::thisproc (HANDLE h)
 {
   procinfo = NULL;
+  bool execed = !!h;
 
   DWORD flags = PID_IN_USE | PID_ACTIVE;
   /* Forked process or process started from non-Cygwin parent needs a pid. */
-  if (!h)
+  if (!execed)
     {
       cygheap->pid = create_cygwin_pid ();
       flags |= PID_NEW;
@@ -72,7 +73,8 @@ pinfo::thisproc (HANDLE h)
   procinfo->dwProcessId = myself_initial.dwProcessId;
   procinfo->sendsig = myself_initial.sendsig;
   wcscpy (procinfo->progname, myself_initial.progname);
-  create_winpid_symlink ();
+  if (!execed)
+    create_winpid_symlink ();
   procinfo->exec_sendsig = NULL;
   procinfo->exec_dwProcessId = 0;
   debug_printf ("myself dwProcessId %u", procinfo->dwProcessId);
diff --git a/winsup/cygwin/release/3.3.6 b/winsup/cygwin/release/3.3.6
index 6d1f0bc8b..6d722433f 100644
--- a/winsup/cygwin/release/3.3.6
+++ b/winsup/cygwin/release/3.3.6
@@ -3,3 +3,7 @@ Bug Fixes
 
 - Fix an issue that command "cmd /c script -c cmd" crashes if it
   is issued in console of Windows 7.
+
+- Fix killpg failing because the exec'ing as well as the exec'ed
+  process are not in the pidlist for a brief moment.
+  Addresses: https://cygwin.com/pipermail/cygwin/2022-May/251479.html
diff --git a/winsup/cygwin/spawn.cc b/winsup/cygwin/spawn.cc
index c9e1fb6d2..e0f1247e1 100644
--- a/winsup/cygwin/spawn.cc
+++ b/winsup/cygwin/spawn.cc
@@ -862,13 +862,14 @@ child_info_spawn::worker (const char *prog_arg, const char *const *argv,
 	  strace.execing = 1;
 	  myself.hProcess = hExeced = pi.hProcess;
 	  HANDLE old_winpid_hdl = myself.shared_winpid_handle ();
-	  if (!real_path.iscygexec ())
-	    {
-	      /* If the child process is not a Cygwin process, we have to
-		 create a new winpid symlink on behalf of the child process
-		 not being able to do this by itself. */
-	      myself.create_winpid_symlink ();
-	    }
+	  /* We have to create a new winpid symlink on behalf of the child
+	     process. For Cygwin processes we also have to create a reference
+	     in the child. */
+	  myself.create_winpid_symlink ();
+	  if (real_path.iscygexec ())
+	    DuplicateHandle (GetCurrentProcess (),
+			     myself.shared_winpid_handle (),
+			     pi.hProcess, NULL, 0, 0, DUPLICATE_SAME_ACCESS);
 	  NtClose (old_winpid_hdl);
 	  real_path.get_wide_win32_path (myself->progname); // FIXME: race?
 	  sigproc_printf ("new process name %W", myself->progname);