5.10-stable review patch. If anyone has any objections, please let me know. ------------------ From: Chris Mason commit be3a5c1d857b0dcbc11796cea603ef25834f75b2 upstream. nfs4_alloc_init_cpntf_state() published the new cpntf entry into the s2s_cp_stateids IDR (with cs_type set) in one s2s_cp_lock section, then took the lock again to list_add() it onto p_stid->sc_cp_list. In the gap the entry is reachable by so_id but cp_list is still {NULL,NULL} from kzalloc. A racing OFFLOAD_CANCEL (so_id is echoed to the client as cnr_stateid, so any NFSv4.2 client can drive it) reaches manage_cpntf_state() -> _free_cpntf_state_locked() and does list_del() on the zeroed list_head, oopsing the server. Fold the cs_type assignment and the list_add() into the same critical section as idr_alloc_cyclic(), so a concurrent lookup either misses the entry or sees a fully linked cp_list. INIT_LIST_HEAD() the entry after allocation and switch _free_cpntf_state_locked() to list_del_init() so a stale unlink is a no-op. nfs4_init_copy_state() passes NULL p_stid and skips the list_add, preserving NFS4_COPY_STID semantics. Fixes: 624322f1adc5 ("NFSD add COPY_NOTIFY operation") Cc: stable@vger.kernel.org Assisted-by: kres:claude-opus-4-7 Signed-off-by: Chris Mason Link: https://patch.msgid.link/20260710-nfsd-testing-v3-1-a0ff7db6aa3e@kernel.org Signed-off-by: Chuck Lever Signed-off-by: Greg Kroah-Hartman --- fs/nfsd/nfs4state.c | 35 +++++++++++++++++++++++++---------- 1 file changed, 25 insertions(+), 10 deletions(-) --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -984,7 +984,7 @@ out_free: * Create a unique stateid_t to represent each COPY. */ static int nfs4_init_cp_state(struct nfsd_net *nn, copy_stateid_t *stid, - unsigned char cs_type) + unsigned char cs_type, struct nfs4_stid *p_stid) { int new_id; @@ -994,19 +994,34 @@ static int nfs4_init_cp_state(struct nfs idr_preload(GFP_KERNEL); spin_lock(&nn->s2s_cp_lock); new_id = idr_alloc_cyclic(&nn->s2s_cp_stateids, stid, 0, 0, GFP_NOWAIT); - stid->cs_stid.si_opaque.so_id = new_id; - stid->cs_stid.si_generation = 1; + if (new_id >= 0) { + stid->cs_stid.si_opaque.so_id = new_id; + stid->cs_stid.si_generation = 1; + /* + * Set cs_type and link onto sc_cp_list under the same lock + * that installed the IDR entry, so a concurrent + * manage_cpntf_state() sees either no entry or a fully + * linked cp_list. + */ + stid->cs_type = cs_type; + if (p_stid) { + struct nfs4_cpntf_state *cps = + container_of(stid, struct nfs4_cpntf_state, + cp_stateid); + + list_add(&cps->cp_list, &p_stid->sc_cp_list); + } + } spin_unlock(&nn->s2s_cp_lock); idr_preload_end(); if (new_id < 0) return 0; - stid->cs_type = cs_type; return 1; } int nfs4_init_copy_state(struct nfsd_net *nn, struct nfsd4_copy *copy) { - return nfs4_init_cp_state(nn, ©->cp_stateid, NFS4_COPY_STID); + return nfs4_init_cp_state(nn, ©->cp_stateid, NFS4_COPY_STID, NULL); } struct nfs4_cpntf_state *nfs4_alloc_init_cpntf_state(struct nfsd_net *nn, @@ -1017,13 +1032,13 @@ struct nfs4_cpntf_state *nfs4_alloc_init cps = kzalloc(sizeof(struct nfs4_cpntf_state), GFP_KERNEL); if (!cps) return NULL; + /* So a stale list_del_init() before linking is a no-op. */ + INIT_LIST_HEAD(&cps->cp_list); cps->cpntf_time = ktime_get_boottime_seconds(); refcount_set(&cps->cp_stateid.cs_count, 1); - if (!nfs4_init_cp_state(nn, &cps->cp_stateid, NFS4_COPYNOTIFY_STID)) + if (!nfs4_init_cp_state(nn, &cps->cp_stateid, NFS4_COPYNOTIFY_STID, + p_stid)) goto out_free; - spin_lock(&nn->s2s_cp_lock); - list_add(&cps->cp_list, &p_stid->sc_cp_list); - spin_unlock(&nn->s2s_cp_lock); return cps; out_free: kfree(cps); @@ -6593,7 +6608,7 @@ _free_cpntf_state_locked(struct nfsd_net WARN_ON_ONCE(cps->cp_stateid.cs_type != NFS4_COPYNOTIFY_STID); if (!refcount_dec_and_test(&cps->cp_stateid.cs_count)) return; - list_del(&cps->cp_list); + list_del_init(&cps->cp_list); idr_remove(&nn->s2s_cp_stateids, cps->cp_stateid.cs_stid.si_opaque.so_id); kfree(cps);