From: Chuck Lever <cel@kernel.org> stable inclusion from stable-v5.10.270 commit 42d7954b0a1907d4ef122aef94561952a033cdc3 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/18929 CVE: CVE-2026-89662 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=... -------------------------------- commit 5e2fa29d223a9a1e6a948e40b109d09081d1decd upstream. __destroy_client() releases a client's open owners, but a lock owner whose only reference is a blocked lock (nbl) stays on cl_ownerstr_hashtbl. client_has_state() does not count a bare owner, so DESTROY_CLIENTID can reach __destroy_client() with such owners present. __destroy_client() then walks the table, calling remove_blocked_locks() on each owner without a reference. Freeing a blocked lock drops the owner reference held via flc_owner. The per-net laundromat reaps blocked locks from nn->blocked_locks_lru independently of client state. The two paths share blocked_locks_lock only for the list splice, not the owner's lifetime. The laundromat therefore frees the owner as __destroy_client() dereferences it, a NULL dereference in remove_blocked_locks(). nfsd4_release_lockowner() holds a reference across the same call; __destroy_client() does not. Hold cl_lock across the walk, taking a reference and unhashing each owner, then drop it before remove_blocked_locks() and nfs4_put_stateowner(), which take blocked_locks_lock and cl_lock. Reported-by: Wolfgang Walter <linux@stwm.de> Closes: https://lore.kernel.org/linux-nfs/6eccafaaaa60651ef091257c3439c46b@stwm.de/ Fixes: 68ef3bc31664 ("nfsd: remove blocked locks on client teardown") Cc: stable@vger.kernel.org Reviewed-by: NeilBrown <neil@brown.name> Reviewed-by: Jeff Layton <jlayton@kernel.org> Link: https://patch.msgid.link/20260709-cel-v4-1-1d519d9be0cb@kernel.org Signed-off-by: Chuck Lever <cel@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Lu Jialin <lujialin4@huawei.com> --- fs/nfsd/nfs4state.c | 16 +++++++++++++--- 1 file changed, 13 insertions(+), 3 deletions(-) diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c index 7bfe0a6bc5fd..f1eef728f157 100644 --- a/fs/nfsd/nfs4state.c +++ b/fs/nfsd/nfs4state.c @@ -2197,14 +2197,24 @@ __destroy_client(struct nfs4_client *clp) release_openowner(oo); } for (i = 0; i < OWNER_HASH_SIZE; i++) { - struct nfs4_stateowner *so, *tmp; + struct nfs4_stateowner *so; - list_for_each_entry_safe(so, tmp, &clp->cl_ownerstr_hashtbl[i], - so_strhash) { + spin_lock(&clp->cl_lock); + while (!list_empty(&clp->cl_ownerstr_hashtbl[i])) { + so = list_first_entry(&clp->cl_ownerstr_hashtbl[i], + struct nfs4_stateowner, so_strhash); /* Should be no openowners at this point */ WARN_ON_ONCE(so->so_is_open_owner); + nfs4_get_stateowner(so); + unhash_lockowner_locked(lockowner(so)); + spin_unlock(&clp->cl_lock); + remove_blocked_locks(lockowner(so)); + nfs4_put_stateowner(so); + + spin_lock(&clp->cl_lock); } + spin_unlock(&clp->cl_lock); } nfsd4_return_all_client_layouts(clp); nfsd4_shutdown_copy(clp); -- 2.34.1