UBUNTU-CVE-2026-98708: High severity ubuntu/linux-aws vulnerability

In the Linux kernel, the following vulnerability has been resolved: wifi: mac80211: keep paired old chanctx alive An in-place replacement keeps reciprocal replacectx pointers between the old WILLBEREPLACED chanctx and the new REPLACESOTHER chanctx. However, the early free paths only consider assigned and reserved link users when deciding whether to free the old chanctx. That lets the old chanctx be freed too early while the replacement partner still points back to it, either when the last assigned link is released or when that link successfully reassigns to another existing context. Later unreserve and switch-finalization paths can then follow a stale replacectx pointer. Keep a paired old chanctx alive until the replacement pair has been torn down. Apply the same check to both ieee80211linkreleasechannel() and ieee80211linkusereservedreassign(). If the replacement is later abandoned, ieee80211linkunreservechanctx() already tears down the pairing before freeing the old chanctx once no users remain.