From cec51c85fa6092c50db2be5e4910ed47d9aebc32 Mon Sep 17 00:00:00 2001
From: Dirk Lemstra <dirk@lemstra.org>
Date: Fri, 1 Jan 2021 15:00:17 +0100
Subject: Fixed possible deadlock when the process is waiting for ImageMagick
 to read the console output.

---
 MagickCore/nt-base.c | 52 ++++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 44 insertions(+), 8 deletions(-)

(limited to 'MagickCore/nt-base.c')

diff --git a/MagickCore/nt-base.c b/MagickCore/nt-base.c
index 79b2b6baa..31b625780 100644
--- a/MagickCore/nt-base.c
+++ b/MagickCore/nt-base.c
@@ -42,6 +42,7 @@
 #if defined(MAGICKCORE_WINDOWS_SUPPORT)
 #include "MagickCore/client.h"
 #include "MagickCore/exception-private.h"
+#include "MagickCore/image-private.h"
 #include "MagickCore/locale_.h"
 #include "MagickCore/log.h"
 #include "MagickCore/magick.h"
@@ -2301,9 +2302,7 @@ MagickPrivate int NTSystemCommand(const char *command,char *output)
     local_command[MagickPathExtent];
 
   DWORD
-    bytes_read,
-    child_status,
-    size;
+    child_status;
 
   int
     status;
@@ -2321,6 +2320,9 @@ MagickPrivate int NTSystemCommand(const char *command,char *output)
   SECURITY_ATTRIBUTES
     sa;
 
+  size_t
+    output_offset;
+
   STARTUPINFO
     startup_info;
 
@@ -2376,9 +2378,47 @@ MagickPrivate int NTSystemCommand(const char *command,char *output)
       CleanupOutputHandles;
       return(-1);
     }
+  if (output != (char *) NULL)
+    *output='\0';
   if (asynchronous != MagickFalse)
     return(status == 0);
-  status=WaitForSingleObject(process_info.hProcess,INFINITE);
+  output_offset=0;
+  status=STATUS_TIMEOUT;
+  while (status == STATUS_TIMEOUT)
+  {
+    DWORD
+      size;
+
+    status=WaitForSingleObject(process_info.hProcess,1000);
+    size=0;
+    if (read_output != (HANDLE) NULL)
+      if (!PeekNamedPipe(read_output,NULL,0,NULL,&size,NULL))
+        break;
+    while (size > 0)
+    {
+      char
+        buffer[MagickPathExtent];
+
+      DWORD
+        bytes_read;
+
+      if (ReadFile(read_output,buffer,sizeof(buffer)-1,&bytes_read,NULL))
+        {
+          size_t
+            count;
+
+          count=MagickMin(MagickPathExtent-1-output_offset,bytes_read);
+          if (count > 0)
+            {
+              CopyMagickString(output+output_offset,buffer,count);
+              output[count]='\0';
+              output_offset=count;
+            }
+        }
+      if (!PeekNamedPipe(read_output,NULL,0,NULL,&size,NULL))
+        break;
+    }
+  }
   if (status != WAIT_OBJECT_0)
     {
       CopyLastError;
@@ -2394,10 +2434,6 @@ MagickPrivate int NTSystemCommand(const char *command,char *output)
     }
   CloseHandle(process_info.hProcess);
   CloseHandle(process_info.hThread);
-  if (read_output != (HANDLE) NULL)
-    if (PeekNamedPipe(read_output,(LPVOID) NULL,0,(LPDWORD) NULL,&size,(LPDWORD) NULL))
-      if ((size > 0) && (ReadFile(read_output,output,MagickPathExtent-1,&bytes_read,NULL)))
-        output[bytes_read]='\0';
   CleanupOutputHandles;
   return((int) child_status);
 }
-- 
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