Open Handle in one Process and Close in another?
in [Win32 Kernel]
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From: David F. on 25 Feb 2010 21:16 Hi, So everything I've read seems to suggest that Handles are global in Windows space and even between x64 and x32 processes. One thing I haven't seen addressed is if opening a handle in one process and then closing in another is allowed or does that create a potential for double closing the handle? I mean the process that opened the handle would automatically close any open handles, but would it know that the handle was closed? If not, I guess if one wanted to transparently use a handle as it would itself one would duplicate the handle from the other process and use then close the duplicated handle and let the other process close the handle it opened. Or pass something other than a handle to a process and open that within the process where it will be used. ? TIA!!
From: Don Burn on 25 Feb 2010 21:37 Handles are unique to processes, there is nothing global about them. When the process that opens the handle terminates they get closed. Passing a handle to another process will just cause it to get an invalid handle or if you are really unlucky the wrong handle. If you want to pass a handle look at the DuplicateHandle function, but this is creating a new handle. Don Burn (MVP, Windows DKD) Windows Filesystem and Driver Consulting Website: http://www.windrvr.com Blog: http://msmvps.com/blogs/WinDrvr "David F." <df2705(a)community.nospam> wrote in message news:B6984F33-F6DE-4283-B036-CACC6767EBCE(a)microsoft.com: > Hi, > > So everything I've read seems to suggest that Handles are global in Windows > space and even between x64 and x32 processes. One thing I haven't seen > addressed is if opening a handle in one process and then closing in another > is allowed or does that create a potential for double closing the handle? I > mean the process that opened the handle would automatically close any open > handles, but would it know that the handle was closed? If not, I guess if > one wanted to transparently use a handle as it would itself one would > duplicate the handle from the other process and use then close the > duplicated handle and let the other process close the handle it opened. Or > pass something other than a handle to a process and open that within the > process where it will be used. > > ? > > TIA!! __________ Information from ESET Smart Security, version of virus signature database 4896 (20100225) __________ The message was checked by ESET Smart Security. http://www.eset.com
From: Jonathan de Boyne Pollard on 26 Feb 2010 03:38 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> <html> <head> <meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type"> </head> <body bgcolor="#ffffff" text="#000000"> <blockquote cite="mid:B6984F33-F6DE-4283-B036-CACC6767EBCE(a)microsoft.com" type="cite"> <p>So everything I've read seems to suggest that Handles are global in Windows space and even between x64 and x32 processes.</p> </blockquote> <p>You haven't read nearly enough. Start with <a href="http://msdn.microsoft.com/en-gb/library/ms724485%28VS.85%29.aspx">the MSDN Libary discussion of kernel objects</a>.</p> </body> </html>
From: David F. on 26 Feb 2010 05:29 I guess it depends on the type of handle: "64-bit versions of Windows use 32-bit handles for interoperability. When sharing a handle between 32-bit and 64-bit applications, only the lower 32 bits are significant, so it is safe to truncate the handle (when passing it from 64-bit to 32-bit) or sign-extend the handle (when passing it from 32-bit to 64-bit). Handles that can be shared include handles to user objects such as windows (HWND), handles to GDI objects such as pens and brushes (HBRUSH and HPEN), and handles to named objects such as mutexes, semaphores, and file handles." From http://msdn.microsoft.com/en-us/library/aa384203(VS.85).aspx "Jonathan de Boyne Pollard" <J.deBoynePollard-newsgroups(a)NTLWorld.COM> wrote in message news:IU.D20100226.T083821.P9445.Q0(a)J.de.Boyne.Pollard.localhost... So everything I've read seems to suggest that Handles are global in Windows space and even between x64 and x32 processes. You haven't read nearly enough. Start with the MSDN Libary discussion of kernel objects.
From: rogero on 26 Feb 2010 09:08
On Feb 26, 10:29 am, "David F." <df2...(a)community.nospam> wrote: > I guess it depends on the type of handle: It depends more on how it is created. If you create a handle with inheritable attributes it is passed down to the child process using the same handle value. However, each process actually has its own handle to the same underlying kernel object and each process must explicitly or implicitly close the handle before the underlying object is released. Simply passing the handle value to another process does not enable the handle to be used by the other process -- in general this value may even be a genuine handle in the target process but not to the same object. Example: parentProcess.exe: HANDLE h1 = OpenMutex(MUTEX_ALL_ACCESS, TRUE, "Global\\RogerOrr"); CreateProcess("childProcess.exe", ...) childProcess.exe: will be created with an already open handle to the mutex with the same numeric value as h1. siblingProcess: HANDLE h2 = OpenMutex(MUTEX_ALL_ACCESS, TRUE, "Global\\RogerOrr"); h2 may or may not have the same numeric value as h1. HTH, Roger. |