Bug 2348658 (CVE-2025-21781)

Summary:	CVE-2025-21781 kernel: batman-adv: fix panic during interface removal
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	dfreiber, drow, jburrell, vkumar
Target Milestone:	---	Keywords:	Security
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Hardware:	All
OS:	Linux
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
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Description OSIDB Bzimport 2025-02-27 03:06:44 UTC

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

batman-adv: fix panic during interface removal

Reference counting is used to ensure that
batadv_hardif_neigh_node and batadv_hard_iface
are not freed before/during
batadv_v_elp_throughput_metric_update work is
finished.

But there isn't a guarantee that the hard if will
remain associated with a soft interface up until
the work is finished.

This fixes a crash triggered by reboot that looks
like this:

Call trace:
 batadv_v_mesh_free+0xd0/0x4dc [batman_adv]
 batadv_v_elp_throughput_metric_update+0x1c/0xa4
 process_one_work+0x178/0x398
 worker_thread+0x2e8/0x4d0
 kthread+0xd8/0xdc
 ret_from_fork+0x10/0x20

(the batadv_v_mesh_free call is misleading,
and does not actually happen)

I was able to make the issue happen more reliably
by changing hardif_neigh->bat_v.metric_work work
to be delayed work. This allowed me to track down
and confirm the fix.

[sven: prevent entering batadv_v_elp_get_throughput without
 soft_iface]

Comment 1 Michal Findra 2025-02-27 13:21:57 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025022607-CVE-2025-21781-7324@gregkh/T