CVE-2022-50307

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> s390/cio: fix out-of-bounds access on cio_ignore free<br /> <br /> The channel-subsystem-driver scans for newly available devices whenever<br /> device-IDs are removed from the cio_ignore list using a command such as:<br /> <br /> echo free &gt;/proc/cio_ignore<br /> <br /> Since an I/O device scan might interfer with running I/Os, commit<br /> 172da89ed0ea ("s390/cio: avoid excessive path-verification requests")<br /> introduced an optimization to exclude online devices from the scan.<br /> <br /> The newly added check for online devices incorrectly assumes that<br /> an I/O-subchannel&amp;#39;s drvdata points to a struct io_subchannel_private.<br /> For devices that are bound to a non-default I/O subchannel driver, such<br /> as the vfio_ccw driver, this results in an out-of-bounds read access<br /> during each scan.<br /> <br /> Fix this by changing the scan logic to rely on a driver-independent<br /> online indication. For this we can use struct subchannel-&gt;config.ena,<br /> which is the driver&amp;#39;s requested subchannel-enabled state. Since I/Os<br /> can only be started on enabled subchannels, this matches the intent<br /> of the original optimization of not scanning devices where I/O might<br /> be running.