configfs-tsm-report: Fix NULL dereference of tsm_ops

Overview

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

configfs-tsm-report: Fix NULL dereference of tsm_ops

Unlike sysfs, the lifetime of configfs objects is controlled by userspace. There is no mechanism for the kernel to find and delete all created config-items. Instead, the configfs-tsm-report mechanism has an expectation that tsm_unregister() can happen at any time and cause established config-item access to start failing.

That expectation is not fully satisfied. While tsm_report_read(), tsm_report_{is,is_bin}_visible(), and tsm_report_make_item() safely fail if tsm_ops have been unregistered, tsm_report_privlevel_store() tsm_report_provider_show() fail to check for ops registration. Add the missing checks for tsm_ops having been removed.

Now, in supporting the ability for tsm_unregister() to always succeed, it leaves the problem of what to do with lingering config-items. The expectation is that the admin that arranges for the ->remove() (unbind) of the ${tsm_arch}-guest driver is also responsible for deletion of all open config-items. Until that deletion happens, ->probe() (reload / bind) of the ${tsm_arch}-guest driver fails.

This allows for emergency shutdown / revocation of attestation interfaces, and requires coordinated restart.

Affected

• Linux >= 70e6f7e2b98575621019aa40ac616be58ff984e0 < 015f04ac884a454d4d8aaa7b67758f047742b1cf
• Linux >= 70e6f7e2b98575621019aa40ac616be58ff984e0 < cefbafcbdef011d6ef9414902311afdfba3c33eb
• Linux >= 70e6f7e2b98575621019aa40ac616be58ff984e0 < fba4ceaa242d2bdf4c04b77bda41d32d02d3925d
• Linux 6.7

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.