CVE-2026-89676nfsd: fix stale s2s_cp_stateids IDR entry for async COPY

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/745b2edfdd96b8738a94dee450adff4c7d026d5b
• https://git.kernel.org/stable/c/bdce362f49410b9def65d76c21f6259cd89696d8
• https://git.kernel.org/stable/c/7aa34ea78f74e6ef60c8112635a87fc43d57f6c9
• https://git.kernel.org/stable/c/9b4e5e9ba5ae13808b8a6d229d87c54611ba0e7a
• https://git.kernel.org/stable/c/14b978e8d05ce018d0afbeb6611833ef91713a02
• https://git.kernel.org/stable/c/d0beaee498e11880e72826026db0e9c9890fc114