Bug 2492089 (CVE-2026-52919)

Summary:	CVE-2026-52919 kernel: batman-adv: fix tp_meter counter underflow during shutdown
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	unspecified	CC:	rhel-process-autobot, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the `batman-adv` module of the Linux kernel. During the shutdown process of the `tp_meter` sender, an atomic counter can underflow due to multiple decrements. This can cause the sender kernel thread to loop indefinitely, leading to a use-after-free vulnerability if the associated network interface is removed. This issue could result in system instability or a denial of service.	Story Points:	---
Clone Of:		Environment:
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Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-06-24 08:01:27 UTC

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

batman-adv: fix tp_meter counter underflow during shutdown

batadv_tp_sender_shutdown() unconditionally decrements the "sending"
atomic counter. If multiple paths (e.g. timeout, user cancel, and
normal finish) call this function, the counter can underflow to -1.

Since the sender logic treats any non-zero value as "still sending",
a negative value causes the sender kthread to loop indefinitely.
This leads to a use-after-free when the interface is removed while
the zombie thread is still active.

Fix this by using atomic_xchg() to ensure the counter only transitions
from 1 to 0 once.

[sven: added missing change in batadv_tp_send]

Comment 1 Mauro Matteo Cascella 2026-06-24 10:12:55 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062430-CVE-2026-52919-f17e@gregkh/T