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.