nfsd: drop the stateid, not the stateowner, on seqid_op replay retry

Summary

In the Linux kernel, the following vulnerability has been resolved: nfsd: drop the stateid, not the stateowner, on seqid_op replay retry In nfs4_preprocess_seqid_op() the stateid is obtained from nfsd4_lookup_stateid(), which holds a reference on the nfs4_stid (sc_count) but takes no reference on the stateowner. openlockstateid() merely casts that stid and likewise takes no reference. When nfsd4_cstate_assign_replay() returns -EAGAIN (the replay owner is being torn down, RP_UNHASHED) it has not taken a stateowner reference on that path. The error handling nevertheless called nfs4_put_stateowner(stp->st_stateowner), dropping an so_count reference the function never acquired -- risking a stateowner refcount underflow and use-after-free -- while leaking the sc_count reference held on the stid. The leaked stid reference can also stall a concurrent nfsd4_close_open_stateid() waiting for sc_count to drop. Drop the reference actually held -- the stid -- before retrying. The stateowner stays alive through the reference held by the stid. This mirrors the open path in nfsd4_process_open1(), where the put balances a reference that path explicitly holds on the stateowner.

Timeline

1. Sep 11, 2026, 7:46 PM UTCCVE published
2. Oct 19, 2026, 8:51 AM UTCRecord last updated

Affected versions

• Linux Linux

  From eec7620800081e27dbf8019ac2e66259f0d5bf6f · fixed in 69ed78b6b947c9257213164678b4edf17533093b; From eec7620800081e27dbf8019ac2e66259f0d5bf6f · fixed in 00843074d9b84824552c9679d423d29500ca5de0; From eec7620800081e27dbf8019ac2e66259f0d5bf6f · fixed in f7cb90ddc021747fc9abfd4cf5252d425fd34eec; From eec7620800081e27dbf8019ac2e66259f0d5bf6f · fixed in 5e4627d3513e60accfce9d5f4c7fa95251ef93d6

• Linux Linux

  6.10

• KernelLinux

  From 6.10.0 · fixed in 6.12.109; From 6.13.0 · fixed in 6.18.50; From 6.19.0 · fixed in 7.2.4

References 4