xcb: Fix access to shm for X server running from another user

Use ShmCreateSegment call, that was added in MIT-SHM 1.2, to
create shared memory segments on the server side. It returns
a POSIX shared memory object that is used to mmap memory.
It's in effect a file descriptor that is passed through the
X server socket and thus avoids permission checks.
On the other hand this scheme is more secure, because the
file descriptor, and thus the shared memory, are accessible
only by the X server and the application.

Task-number: QTBUG-46017
Change-Id: I202eead9d01aee2ab5b65f4f74f4c13da7cb2239
Reviewed-by: Gatis Paeglis <gatis.paeglis@qt.io>

0 files changed, 0 insertions, 0 deletions