CVE-2026-68176

In the Linux kernel, the following vulnerability has been resolved:

tracing: Fix mmiotrace possible NULL dereferencing of hiter->dev

If the mmio_pipe_open() fails to find a PCI device, the hiter->dev
will be assigned to NULL. The mmiotrace read() function dereferences the
hiter->dev if hiter exists.

Change the test of the read to not only check hiter being NULL, but also
the hiter->dev before dereferencing it.