CVE-2022-50307

/// Technical description

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

s390/cio: fix out-of-bounds access on cio_ignore free

The channel-subsystem-driver scans for newly available devices whenever

device-IDs are removed from the cio_ignore list using a command such as:

echo free >/proc/cio_ignore

Since an I/O device scan might interfer with running I/Os, commit

172da89ed0ea ("s390/cio: avoid excessive path-verification requests")

introduced an optimization to exclude online devices from the scan.

The newly added check for online devices incorrectly assumes that

an I/O-subchannel's drvdata points to a struct io_subchannel_private.

For devices that are bound to a non-default I/O subchannel driver, such

as the vfio_ccw driver, this results in an out-of-bounds read access

during each scan.

Fix this by changing the scan logic to rely on a driver-independent

online indication. For this we can use struct subchannel->config.ena,

which is the driver's requested subchannel-enabled state. Si

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References