Bug 2554926 (CVE-2026-98623)

Summary:	CVE-2026-98623 kernel: drm/nouveau/clk: fix list cursor use after loop in nvkm_clk_ustate_update
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:	akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, 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 Nouveau driver. A local user can trigger an out-of-bounds read by requesting an invalid clock performance state through the debugfs interface. This issue can lead to a system crash, resulting in a Denial of Service (DoS).	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 2026-10-18 15:33:09 UTC

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

drm/nouveau/clk: fix list cursor use after loop in nvkm_clk_ustate_update

If list_for_each_entry() exits without hitting a break then "pstate" is
not a valid pstate pointer.  Introduce a "found" variable instead.

The check is reachable from userspace: nvkm_clk_ustate_update() takes the
pstate id straight from the 'pstate' debugfs file, so requesting an id
that is not in clk->states - or any id at all when the perf tables are
broken and the list is empty - makes the pstate->pstate != req test
dereference the list head cast to a struct nvkm_pstate, which is an
out-of-bounds read.

[Francesco: rebased on drm-misc-next, expanded the commit message]