From 7c4a774e4eb9dfdf9271b6bbef2bb1b5191db398 Mon Sep 17 00:00:00 2001
From: David Fort <contact@hardening-consulting.com>
Date: Fri, 3 Mar 2023 15:45:15 +0100
Subject: [PATCH] winpr: fix WaitForMultipleObjectsEx(alertable) call from non
 winpr threads

When WaitForMultipleObjectsEx is called with the alertable flag set from a non
WinPR thread, we shall not try to treat APC, as for sure there is no APC scheduled,
as previous call that would have scheduled such APC would have failed.
---
 winpr/libwinpr/synch/sleep.c | 14 ++++++------
 winpr/libwinpr/synch/wait.c  | 41 +++++++++++++++++++++---------------
 2 files changed, 32 insertions(+), 23 deletions(-)

diff --git a/winpr/libwinpr/synch/sleep.c b/winpr/libwinpr/synch/sleep.c
index 95e9eed51..14950884a 100644
--- a/winpr/libwinpr/synch/sleep.c
+++ b/winpr/libwinpr/synch/sleep.c
@@ -63,15 +63,17 @@ DWORD SleepEx(DWORD dwMilliseconds, BOOL bAlertable)
 	DWORD ret = WAIT_FAILED;
 	BOOL autoSignalled;
 
-	if (!thread)
+	if (thread)
 	{
-		WLog_ERR(TAG, "unable to retrieve currentThread");
-		return WAIT_FAILED;
+		/* treat re-entrancy if a completion is calling us */
+		if (thread->apc.treatingCompletions)
+			bAlertable = FALSE;
 	}
-
-	/* treat re-entrancy if a completion is calling us */
-	if (thread->apc.treatingCompletions)
+	else
+	{
+		/* called from a non WinPR thread */
 		bAlertable = FALSE;
+	}
 
 	if (!bAlertable || !thread->apc.length)
 	{
diff --git a/winpr/libwinpr/synch/wait.c b/winpr/libwinpr/synch/wait.c
index 8c442a50d..66a06f992 100644
--- a/winpr/libwinpr/synch/wait.c
+++ b/winpr/libwinpr/synch/wait.c
@@ -263,18 +263,20 @@ DWORD WaitForSingleObjectEx(HANDLE hHandle, DWORD dwMilliseconds, BOOL bAlertabl
 		if (bAlertable)
 		{
 			thread = (WINPR_THREAD*)_GetCurrentThread();
-			if (!thread)
+			if (thread)
 			{
-				WLog_ERR(TAG, "failed to retrieve currentThread");
-				return WAIT_FAILED;
+				/* treat reentrancy, we can't switch to alertable state when we're already
+				   treating completions */
+				if (thread->apc.treatingCompletions)
+					bAlertable = FALSE;
+				else
+					extraFds = thread->apc.length;
 			}
-
-			/* treat reentrancy, we can't switch to alertable state when we're already
-			   treating completions */
-			if (thread->apc.treatingCompletions)
-				bAlertable = FALSE;
 			else
-				extraFds = thread->apc.length;
+			{
+				/* called from a non WinPR thread */
+				bAlertable = FALSE;
+			}
 		}
 
 		int fd = winpr_Handle_getFd(Object);
@@ -365,15 +367,20 @@ DWORD WaitForMultipleObjectsEx(DWORD nCount, const HANDLE* lpHandles, BOOL bWait
 	if (bAlertable)
 	{
 		thread = winpr_GetCurrentThread();
-		if (!thread)
-			return WAIT_FAILED;
-
-		/* treat reentrancy, we can't switch to alertable state when we're already
-		   treating completions */
-		if (thread->apc.treatingCompletions)
-			bAlertable = FALSE;
+		if (thread)
+		{
+			/* treat reentrancy, we can't switch to alertable state when we're already
+			   treating completions */
+			if (thread->apc.treatingCompletions)
+				bAlertable = FALSE;
+			else
+				extraFds = thread->apc.length;
+		}
 		else
-			extraFds = thread->apc.length;
+		{
+			/* most probably we're not called from WinPR thread, so we can't have any APC */
+			bAlertable = FALSE;
+		}
 	}
 
 	if (!pollset_init(&pollset, nCount + extraFds))