CVE-2026-53399

Summary

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

nfsd: release layout stid on setlease failure

nfs4_alloc_stid() publishes the new stid into cl->cl_stateids via idr_alloc_cyclic() under cl_lock before returning to nfsd4_alloc_layout_stateid(). When nfsd4_layout_setlease() then fails, the error path frees the layout stateid directly with kmem_cache_free() without ever calling idr_remove(), leaving the IDR slot pointing at freed slab memory. Any subsequent IDR walker (states_show, client teardown) dereferences the dangling pointer.

The correct teardown for an IDR-published stid is nfs4_put_stid(), which removes the IDR slot under cl_lock, dispatches sc_free (nfsd4_free_layout_stateid) to release ls->ls_file via nfsd4_close_layout(), and drops the nfs4_file reference in its tail.

A second issue blocks that switch: nfsd4_free_layout_stateid() unconditionally inspects ls->ls_fence_work via delayed_work_pending() under ls_lock, but INIT_DELAYED_WORK(&ls->ls_fence_work, …) currently runs only after the setlease call. On the setlease-failure path the destructor would touch an uninitialized delayed_work.

nfsd4_alloc_layout_stateid()
  nfs4_alloc_stid()           /* idr_alloc_cyclic under cl_lock */
  nfsd4_layout_setlease()     /* fails */
    nfs4_put_stid()
      nfsd4_free_layout_stateid()
        delayed_work_pending(&ls->ls_fence_work)  /* needs INIT */
        nfsd4_close_layout()  /* nfsd_file_put(ls->ls_file) */
      put_nfs4_file()

Fix by hoisting the ls_fenced / ls_fence_delay / INIT_DELAYED_WORK initialization above the nfsd4_layout_setlease() call, and replace the manual nfsd_file_put + put_nfs4_file + kmem_cache_free cleanup with a single nfs4_put_stid(stp).

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/d369e5edfaaf83a448016e2f1da392b2174be801
• https://git.kernel.org/stable/c/8dee7c278f1c2b5bb80e17a6281c3812fc8b0cdd
• https://git.kernel.org/stable/c/83c2b7797742339bb768f83935f7ca33950db138
• https://git.kernel.org/stable/c/30d55c8aabb261bc3f427d6b9aae7ef6206063f9

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