[PATCH v2] Cygwin: Fix the address of myself

Corinna Vinschen corinna-cygwin@cygwin.com
Wed Jul 24 16:54:00 GMT 2019


From: Corinna Vinschen <corinna@vinschen.de>

v2: rephrase commit message

Introducing an independent Cygwin PID introduced a regression:

The expectation is that the myself pinfo pointer always points to a
specific address right in front of the loaded Cygwin DLL.

However, the independent Cygwin PID changes broke this.  To create
myself at the right address requires to call init with h0 set to
INVALID_HANDLE_VALUE or an existing address:

void
pinfo::init (pid_t n, DWORD flag, HANDLE h0)
{
  [...]
  if (!h0 || myself.h)
    [...]
  else
    {
      shloc = SH_MYSELF;
      if (h0 == INVALID_HANDLE_VALUE)       <-- !!!
        h0 = NULL;
    }

The aforementioned commits changed that so h0 was always NULL, this way
creating myself at an arbitrary address.

This patch makes sure to set the handle to INVALID_HANDLE_VALUE again
when creating a new process, so init knows that myself has to be created
in the right spot.  While at it, fix a potential uninitialized handle
value in child_info_spawn::handle_spawn.

Fixes: b5e1003722cb ("Cygwin: processes: use dedicated Cygwin PID rather than Windows PID")
Fixes: 88605243a19b ("Cygwin: fix child getting another pid after spawnve")
Signed-off-by: Corinna Vinschen <corinna@vinschen.de>
---
 winsup/cygwin/dcrt0.cc | 2 +-
 winsup/cygwin/pinfo.cc | 3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/winsup/cygwin/dcrt0.cc b/winsup/cygwin/dcrt0.cc
index fb726a739ccf..86ab7256484c 100644
--- a/winsup/cygwin/dcrt0.cc
+++ b/winsup/cygwin/dcrt0.cc
@@ -652,7 +652,7 @@ void
 child_info_spawn::handle_spawn ()
 {
   extern void fixup_lockf_after_exec (bool);
-  HANDLE h;
+  HANDLE h = INVALID_HANDLE_VALUE;
   if (!dynamically_loaded || get_parent_handle ())
       {
 	cygheap_fixup_in_child (true);
diff --git a/winsup/cygwin/pinfo.cc b/winsup/cygwin/pinfo.cc
index cdbd8bd7eaf3..b67d660ae04d 100644
--- a/winsup/cygwin/pinfo.cc
+++ b/winsup/cygwin/pinfo.cc
@@ -62,11 +62,10 @@ pinfo::thisproc (HANDLE h)
     {
       cygheap->pid = create_cygwin_pid ();
       flags |= PID_NEW;
+      h = INVALID_HANDLE_VALUE;
     }
   /* spawnve'd process got pid in parent, cygheap->pid has been set in
      child_info_spawn::handle_spawn. */
-  else if (h == INVALID_HANDLE_VALUE)
-    h = NULL;
 
   init (cygheap->pid, flags, h);
   procinfo->process_state |= PID_IN_USE;
-- 
2.20.1



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