ntdll: Check buffer for access in NtWriteFile before performing I/O.

This also triggers page faults needed for DIB section access.

dlls/ntdll/file.c

@@ -904,6 +904,12 @@ NTSTATUS WINAPI NtWriteFile(HANDLE hFile, HANDLE hEvent,
                                  &needs_close, &type, &options );
     if (status) return status;
 
+    if (!virtual_check_buffer_for_read( buffer, length ))
+    {
+        status = STATUS_INVALID_USER_BUFFER;
+        goto done;
+    }
+
     if (type == FD_TYPE_FILE && offset && offset->QuadPart != (LONGLONG)-2 /* FILE_USE_FILE_POINTER_POSITION */ )
     {
         /* async I/O doesn't make sense on regular files */
@@ -944,19 +950,15 @@ NTSTATUS WINAPI NtWriteFile(HANDLE hFile, HANDLE hEvent,
             }
             if (type == FD_TYPE_FILE) continue;  /* no async I/O on regular files */
         }
-        else
+        else if (errno != EAGAIN)
         {
             if (errno == EINTR) continue;
-            if (errno != EAGAIN)
+            if (!total)
             {
-                if (errno == EFAULT)
-                {
-                    status = STATUS_INVALID_USER_BUFFER;
-                    goto err;
-                }
-                status = FILE_GetNtStatus();
-                goto done;
+                if (errno == EFAULT) status = STATUS_INVALID_USER_BUFFER;
+                else status = FILE_GetNtStatus();
             }
+            goto done;
         }
 
         if (!(options & (FILE_SYNCHRONOUS_IO_ALERT | FILE_SYNCHRONOUS_IO_NONALERT)))

dlls/ntdll/ntdll_misc.h

@@ -141,6 +141,7 @@ extern NTSTATUS virtual_alloc_thread_stack( void *base, SIZE_T stack_size );
 extern void virtual_clear_thread_stack(void);
 extern BOOL virtual_handle_stack_fault( void *addr );
 extern NTSTATUS virtual_handle_fault( LPCVOID addr, DWORD err );
+extern BOOL virtual_check_buffer_for_read( const void *ptr, SIZE_T size );
 extern void VIRTUAL_SetForceExec( BOOL enable );
 extern void VIRTUAL_UseLargeAddressSpace(void);
 extern struct _KUSER_SHARED_DATA *user_shared_data;

dlls/ntdll/virtual.c

@@ -53,6 +53,7 @@
 #include "winternl.h"
 #include "wine/library.h"
 #include "wine/server.h"
+#include "wine/exception.h"
 #include "wine/list.h"
 #include "wine/debug.h"
 #include "ntdll_misc.h"
@@ -1515,6 +1516,40 @@ BOOL virtual_handle_stack_fault( void *addr )
 }
 
 
+/***********************************************************************
+ *           virtual_check_buffer_for_read
+ *
+ * Check if a memory buffer can be read, triggering page faults if needed for DIB section access.
+ */
+BOOL virtual_check_buffer_for_read( const void *ptr, SIZE_T size )
+{
+    if (!size) return TRUE;
+    if (!ptr) return FALSE;
+
+    __TRY
+    {
+        volatile const char *p = ptr;
+        char dummy;
+        SIZE_T count = size;
+
+        while (count > page_size)
+        {
+            dummy = *p;
+            p += page_size;
+            count -= page_size;
+        }
+        dummy = p[0];
+        dummy = p[count - 1];
+    }
+    __EXCEPT_PAGE_FAULT
+    {
+        return FALSE;
+    }
+    __ENDTRY
+    return TRUE;
+}
+
+
 /***********************************************************************
  *           VIRTUAL_SetForceExec
  *