CVE-2021-47369

/// Technical description

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

s390/qeth: fix NULL deref in qeth_clear_working_pool_list()

When qeth_set_online() calls qeth_clear_working_pool_list() to roll

back after an error exit from qeth_hardsetup_card(), we are at risk of

accessing card->qdio.in_q before it was allocated by

qeth_alloc_qdio_queues() via qeth_mpc_initialize().

qeth_clear_working_pool_list() then dereferences NULL, and by writing to

queue->bufs[i].pool_entry scribbles all over the CPU's lowcore.

Resulting in a crash when those lowcore areas are used next (eg. on

the next machine-check interrupt).

Such a scenario would typically happen when the device is first set

online and its queues aren't allocated yet. An early IO error or certain

misconfigs (eg. mismatched transport mode, bad portno) then cause us to

error out from qeth_hardsetup_card() with card->qdio.in_q still being

NULL.

Fix it by checking the pointer for NULL before accessing it.

Note that we also have (rare) pa

/// 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