Bug 2532164 (CVE-2026-89545)

Summary:	CVE-2026-89545 kernel: sunrpc: defer rq_argp and rq_resp free until after RCU grace period
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
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. This vulnerability exists within the `sunrpc` component, where memory associated with `rq_argp` and `rq_resp` is freed prematurely. Specifically, the `svc_rqst_free()` function frees these structures synchronously, while the main request structure (`rqstp`) is freed later via `kfree_rcu()`. This timing issue creates a window where RCU (Read-Copy-Update) readers can still access the already freed `rq_argp` and `rq_resp` pointers, leading to a use-after-free condition. This memory corruption can result in system instability or potentially lead to further exploitation.	Story Points:	---
Clone Of:		Environment:
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-09-11 21:03:23 UTC

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

sunrpc: defer rq_argp and rq_resp free until after RCU grace period

svc_rqst_free() frees rqstp->rq_argp and rqstp->rq_resp synchronously
via kfree(), but defers the rqstp struct free via kfree_rcu().  After
svc_exit_thread() calls list_del_rcu() and svc_rqst_free(), there is
a window where RCU readers that started before list_del_rcu() can still
traverse the thread list and find the rqstp.  These readers (e.g.
nfsd_nl_rpc_status_get_dumpit()) dereference rqstp->rq_argp, which has
already been freed — a use-after-free.

Fix this by moving the kfree of rq_argp and rq_resp into an explicit
call_rcu() callback alongside the struct free.  Resources not accessed
by RCU readers (bvec, buffer pages, scratch folio, auth_data) remain
synchronously freed.

Comment 1 Keith Grant 2026-09-18 15:07:38 UTC

Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89545.mbox