In the Linux kernel, the following vulnerability has been resolved: liveupdate: Remember FLB retrieve() status LUO keeps track of successful retrieve attempts on an FLB

Overview

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

liveupdate: Remember FLB retrieve() status

LUO keeps track of successful retrieve attempts on an FLB. It does so to avoid multiple retrievals of the same FLB. Multiple retrievals cause problems because once the FLB is retrieved, the serialized data structures are likely freed and the FLB is likely in a very different state from what the code expects.

All this works well when retrieve succeeds. When it fails, luo_flb_retrieve_one() returns the error immediately, without ever storing anywhere that a retrieve was attempted or what its error code was. If the user attempts to retrieve another file registered with the same FLB, LUO will attempt to call the FLB's retrieve() callback again.

The retry is problematic for much of the same reasons listed above. The FLB is likely in a very different state than what the retrieve logic normally expects (e.g. some KHO pages may have already been restored and freed).

There is no sane way of attempting the retrieve again. Remember the error retrieve returned and directly return it on a retry.

This is done by changing the retrieved bool to a retrieve_status integer. A value of 0 means retrieve was never attempted, a positive value means it succeeded, and a negative value means it failed and the error code is the value.

This is similar to commit f85b1c6af5bc ("liveupdate: luo_file: remember retrieve() status") which did the same for LUO files.

Remediation

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