Kristian Høgsberg <[email protected]> writes: > On Thu, Oct 31, 2013 at 3:43 PM, Keith Packard <[email protected]> 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. -- [email protected]
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