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

Type: advisorySources: OSV

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.

Products
Kernel
Affected versions
Not specified
Fixed versions
5.10.259, 5.15.210, 6.1.176, 6.12.93, 6.18.34, 6.6.143, 7.0.11
CVEs
CVE-2026-64095
Confirmed fixed CVEs
Not specified
Updated in this feed
2 Nov 2026, 18:28 UTC · Revision 1

Source evidence

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

core-osv · Original source

Published 19 Jul 2026, 15:40 UTC

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.

osv:CVE-2026-64095

Kernel

Fixed versions: 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.93, 6.18.34, 7.0.11

Complete source record
{
  "id": "4ebd5d3c5ba7f4b08dcb37aa20177944b9f02be139a29cb8de50d7c5b52d69ea",
  "url": "https://osv.dev/vulnerability/CVE-2026-64095",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "batman-adv: bla: avoid double decrement of bla.num_requests",
    "summary": "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.",
    "evidence": "osv:CVE-2026-64095",
    "products": [
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                  "introduced": "3.5.0"
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      ],
      "modified": "2026-10-28T02:30:22.240371199Z",
      "provider": "osv",
      "references": [
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        "https://git.kernel.org/stable/c/a9393751ecf7e9096f93cb6eed02db4f79125765",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64095.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-64095",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
        "cna_assigner": "Linux",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64095.json"
      }
    },
    "related_cves": [
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 488424,
  "published_at": "2026-07-19T15:40:02.36+00:00"
}