CVE-2023-54269

/// Technical description

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.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References