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.

https://git.kernel.org/stable/c/1f013bc94154f2e78e97d0296175664224c796e0

https://git.kernel.org/stable/c/45384612f29692fbf0c770200361a7acff90125c

https://git.kernel.org/stable/c/461f1e3dfb888701895b766446c55db2b10db705

https://git.kernel.org/stable/c/5328b95960774f2e189f22485616bc7b8eb2f7e3

https://git.kernel.org/stable/c/65497ad155a3246df177b5ef662cd6e5a32cb470

https://git.kernel.org/stable/c/83ab69bd12b80f6ea169c8bea6977701b53a043d

https://git.kernel.org/stable/c/8ff9c59d1b7b48c2596878341a5310f32895d52b

https://git.kernel.org/stable/c/a9393751ecf7e9096f93cb6eed02db4f79125765

[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","programFiles":["net/batman-adv/bridge_loop_avoidance.c","net/batman-adv/mesh-interface.c","net/batman-adv/types.h"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","versions":[{"version":"23721387c409087fd3b97e274f34d3ddc0970b74","lessThan":"1f013bc94154f2e78e97d0296175664224c796e0","versionType":"git","status":"affected"},{"version":"23721387c409087fd3b97e274f34d3ddc0970b74","lessThan":"5328b95960774f2e189f22485616bc7b8eb2f7e3","versionType":"git","status":"affected"},{"version":"23721387c409087fd3b97e274f34d3ddc0970b74","lessThan":"8ff9c59d1b7b48c2596878341a5310f32895d52b","versionType":"git","status":"affected"},{"version":"23721387c409087fd3b97e274f34d3ddc0970b74","lessThan":"a9393751ecf7e9096f93cb6eed02db4f79125765","versionType":"git","status":"affected"},{"version":"23721387c409087fd3b97e274f34d3ddc0970b74","lessThan":"461f1e3dfb888701895b766446c55db2b10db705","versionType":"git","status":"affected"},{"version":"23721387c409087fd3b97e274f34d3ddc0970b74","lessThan":"45384612f29692fbf0c770200361a7acff90125c","versionType":"git","status":"affected"},{"version":"23721387c409087fd3b97e274f34d3ddc0970b74","lessThan":"65497ad155a3246df177b5ef662cd6e5a32cb470","versionType":"git","status":"affected"},{"version":"23721387c409087fd3b97e274f34d3ddc0970b74","lessThan":"83ab69bd12b80f6ea169c8bea6977701b53a043d","versionType":"git","status":"affected"}]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","programFiles":["net/batman-adv/bridge_loop_avoidance.c","net/batman-adv/mesh-interface.c","net/batman-adv/types.h"],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","versions":[{"version":"3.5","status":"affected"},{"version":"0","lessThan":"3.5","versionType":"semver","status":"unaffected"},{"version":"5.10.259","lessThanOrEqual":"5.10.*","versionType":"semver","status":"unaffected"},{"version":"5.15.210","lessThanOrEqual":"5.15.*","versionType":"semver","status":"unaffected"},{"version":"6.1.176","lessThanOrEqual":"6.1.*","versionType":"semver","status":"unaffected"},{"version":"6.6.143","lessThanOrEqual":"6.6.*","versionType":"semver","status":"unaffected"},{"version":"6.12.93","lessThanOrEqual":"6.12.*","versionType":"semver","status":"unaffected"},{"version":"6.18.34","lessThanOrEqual":"6.18.*","versionType":"semver","status":"unaffected"},{"version":"7.0.11","lessThanOrEqual":"7.0.*","versionType":"semver","status":"unaffected"},{"version":"7.1","lessThanOrEqual":"*","versionType":"original_commit_for_fix","status":"unaffected"}]}]