CVE-2026-97922

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

tracing: Free histogram var refs regardless of how often they are referenced

Using the same variable three or more times in one hist trigger leaks the variable reference and its strings when the trigger is removed.

commit 656fe2ba85e8 ("tracing: Use hist trigger's var ref array to destroy var refs") made a trigger's var refs[] array the only owner of a var ref: destroy hist field() returns early for HIST FIELD FL VAR REF, so the field expressions never destroy one. One entry, freed once, no count needed.

commit 8bcebc77e85f ("tracing: Fix histogram code when expression has same var as value") then made repeated references share one object and added a count of them. Only the increment side exists, since those expressions still return early and never drop a reference, so destroy hist field() sees how many references were created rather than how many are left. It frees when the decremented count is 0 or 1, so two references work and three or more leak.

Sharing kept one array entry per object, and create var ref() searches and appends within a single trigger, so nothing outside it holds the object. Removing a trigger whose variables are still referenced is already refused by check var refs() with -EBUSY. Drop the count and free unconditionally.