CVE-2026-89676

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

nfsd: fix stale s2s cp stateids IDR entry for async COPY

For an async COPY, nfsd4 copy() called nfs4 init copy state() before dup copy fields(), so the s2s cp stateids IDR was pointed at &u->copy->cp stateid -- memory in the per-rqstp COMPOUND buffer that is reused by the next request. dup copy fields() copies only the value into async copy, so the IDR slot dangled at the transient buffer for the whole background copy. Any IDR walker then dereferences reused request memory: the laundromat reads cs type from it and, if the bytes look like an expired NFS4 COPYNOTIFY STID, follows into refcount dec()/idr remove()/kfree() on garbage; manage cpntf state() has the same exposure via idr find().

Duplicate the fields first, then register the stateid on the stable async copy. result->cb stateid is unchanged.