CVE-2026-64095

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

batman-adv: bla: avoid double decrement of bla.num_requests

The bla.num_requests is increased when no request_sent was in progress. And

it is decremented in various places (announcement was received, backbone is

purged, periodic work). But the check if the request_sent is actually set

to a specific state and the atomic_dec/_inc are not safe because they are

not atomic (TOCTOU) and multiple such code portions can run concurrently.

At the same time, it is necessary to modify request_sent (state) and

bla.num_requests atomically. Otherwise batadv_bla_send_request() might set

request_sent to 1 and is interrupted. batadv_handle_announce() can then

set request_sent back to 0 and decrement num_requests before

batadv_bla_send_request() incremented it.

The two operations must therefore be locked. And since state (request_sent)

and wait_periods are only accessed inside this lock, they can be converted

to simpler datatypes. And to avoid that the bla.num_requests is touched by

a parallel running context with a valid backbone_gw reference after

batadv_bla_purge_backbone_gw() ran, a third state "stopped" is required to

correctly signal that a backbone_gw is in the state of being cleaned up.