[newlib-cygwin] flock: Fix hang in object collision case

[Corinna Vinschen <corinna at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=newlib-cygwin.git;h=914620a7e6be4011fadebc7e1f23ed1d0e9ed4d7

commit 914620a7e6be4011fadebc7e1f23ed1d0e9ed4d7
Author: Corinna Vinschen <corinna@vinschen.de>
Date:   Thu Nov 12 13:14:08 2015 +0100

    flock: Fix hang in object collision case
    
    	* flock.cc (lockf_t::create_lock_obj): Correctly recreate lock object
    	attributes anew in each loop.
    
    Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

Diff:
---
 winsup/cygwin/ChangeLog     | 5 +++++
 winsup/cygwin/flock.cc      | 4 ++--
 winsup/cygwin/release/2.3.1 | 5 +++++
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index 8e40c2f..bdaab40 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,5 +1,10 @@
 2015-11-12  Corinna Vinschen  <corinna@vinschen.de>
 
+	* flock.cc (lockf_t::create_lock_obj): Correctly recreate lock object
+	attributes anew in each loop.
+
+2015-11-12  Corinna Vinschen  <corinna@vinschen.de>
+
 	* init.cc (munge_threadfunc): Don't call NtQueryInformationThread with
 	ThreadQuerySetWin32StartAddress info class on XP 64 and Server 2003 64.
 	It crashes.
diff --git a/winsup/cygwin/flock.cc b/winsup/cygwin/flock.cc
index 0ac5548..f7c04c8 100644
--- a/winsup/cygwin/flock.cc
+++ b/winsup/cygwin/flock.cc
@@ -766,12 +766,12 @@ lockf_t::create_lock_obj ()
 {
   lockfattr_t attr;
   NTSTATUS status;
+  PSECURITY_DESCRIPTOR sd_buf = alloca (SD_MIN_SIZE);
   POBJECT_ATTRIBUTES lock_obj_attr;
 
-  lock_obj_attr = create_lock_obj_attr (&attr, OBJ_INHERIT,
-					alloca (SD_MIN_SIZE));
   do
     {
+      lock_obj_attr = create_lock_obj_attr (&attr, OBJ_INHERIT, sd_buf);
       status = NtCreateEvent (&lf_obj, CYG_EVENT_ACCESS, lock_obj_attr,
 			      NotificationEvent, FALSE);
       if (!NT_SUCCESS (status))
diff --git a/winsup/cygwin/release/2.3.1 b/winsup/cygwin/release/2.3.1
index 5299d23..a552ee8 100644
--- a/winsup/cygwin/release/2.3.1
+++ b/winsup/cygwin/release/2.3.1
@@ -12,3 +12,8 @@ Bug Fixes
 - The fix for wine introduced in 2.3.0 crashes in 32 bit Cygwin on 64 bit XP
   and 64 bit Server 2003 only.   This should work now.
   Addresses: https://cygwin.com/ml/cygwin/2015-11/msg00187.html
+
+- The fix to avoid a potential crash in advisory file locking introduced in
+  2.3.0 waas not entirely correct and failed to work in certain border cases.
+  This should work now.
+  Addresses: https://cygwin.com/ml/cygwin/2015-11/msg00189.html