[PATCH 08/10] Add support for MIT-SHM AttachFd request

[Keith Packard]

Kristian Høgsberg <krh at bitplanet.net> writes:

> On Thu, Oct 31, 2013 at 3:43 PM, Keith Packard <keithp at keithp.com> wrote:
>> This passes a file descriptor from the client to the server, which is
>> then mmap'd
>
> A problem we recently hit in wayland, which also affects this
> extension is that a client can set up shared memory like this and the
> truncate the tmp file to 0.  When the server then tries to access the
> mapped memory it dies with SIGBUS.  We're planning on handling this
> case by installing a SIGBUS handler that flags the error, maps
> /dev/zero over the faulting mmap area and then lets the access
> continue.  We'll wrap access the the map with call to begin/end access
> functions and in the end_access function we check the flag to see if
> the access cause a fault and kill the client in that case.

Thanks; I'll have to think about how to handle this in the X server
case.

-- 
keith.packard at intel.com
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