Bug 2516637 (CVE-2026-72117)

Summary:	CVE-2026-72117 kernel: can: bcm: fix data race on rx_stamp/rx_ifindex in bcm_rx_handler()
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	low	Docs Contact:
Priority:	low
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 Linux kernel's CAN (Controller Area Network) Broadcast Manager (BCM) module. A data race condition exists in the `bcm_rx_handler()` function where the `rx_stamp` and `rx_ifindex` values are written without proper locking. This can lead to a "torn store" of the 64-bit `rx_stamp` on 32-bit systems, resulting in the `bcm_send_to_user()` function reporting incorrect timestamp or interface index information for received frames. This issue primarily affects the accuracy of metadata associated with CAN frames.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-08-15 06:23:13 UTC

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

can: bcm: fix data race on rx_stamp/rx_ifindex in bcm_rx_handler()

For an rx op subscribed on all interfaces (ifindex == 0), the same op
is registered once in the shared per-netns wildcard filter list, so
bcm_rx_handler() can run concurrently on different CPUs for frames
arriving on different net devices.

op->rx_stamp and op->rx_ifindex were written before bcm_rx_update_lock was
taken, allowing concurrent writers to race each other - including a torn
store of the 64-bit rx_stamp on 32-bit platforms.

Beyond a torn store bcm_send_to_user() must report the timestamp/ifindex
of the very same frame whose content it is delivering. So the assignment
is placed in the same unbroken bcm_rx_update_lock section as the content
comparison.

As a side effect, the RTR-request frame feature (which never reach
bcm_send_to_user()) no longer updates rx_stamp/rx_ifindex, since only
the notification path needs them.

Comment 1 Keith Grant 2026-08-17 22:31:42 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026081527-CVE-2026-72117-a35b@gregkh/T