Bug 2426013 (CVE-2023-54269)

Summary:	CVE-2023-54269 kernel: SUNRPC: double free xprt_ctxt while still in use
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	Keywords:	Security
Target Milestone:	---
Target Release:	---
Hardware:	All
OS:	Linux
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Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was addressed in the Linux kernel’s SUNRPC implementation affecting deferred RPC request handling. When an RPC request is deferred, the internal rq_xprt_ctxt pointer is moved from the active service request to a deferred request structure. Under certain rare conditions where a request is deferred multiple times, the old context pointer is not cleared before reuse. This can lead to the context being freed twice while still referenced, causing memory corruption and likely resulting in a kernel oops/crash	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 2025-12-30 13:02:00 UTC

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

SUNRPC: double free xprt_ctxt while still in use

When an RPC request is deferred, the rq_xprt_ctxt pointer is moved out
of the svc_rqst into the svc_deferred_req.
When the deferred request is revisited, the pointer is copied into
the new svc_rqst - and also remains in the svc_deferred_req.

In the (rare?) case that the request is deferred a second time, the old
svc_deferred_req is reused - it still has all the correct content.
However in that case the rq_xprt_ctxt pointer is NOT cleared so that
when xpo_release_xprt is called, the ctxt is freed (UDP) or possible
added to a free list (RDMA).
When the deferred request is revisited for a second time, it will
reference this ctxt which may be invalid, and the free the object a
second time which is likely to oops.

So change svc_defer() to *always* clear rq_xprt_ctxt, and assert that
the value is now stored in the svc_deferred_req.

Comment 1 Alexander B 2025-12-31 15:43:25 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025123000-CVE-2023-54269-6fd7@gregkh/T