6.1-stable review patch. If anyone has any objections, please let me know.
------------------
From: Chuck Lever <cel@kernel.org>
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 <redacted>
Closes: https://lore.kernel.org/linux-nfs/6eccafaaaa60651ef091257c3439c46b@stwm.de/ (local)
Fixes: 68ef3bc31664 ("nfsd: remove blocked locks on client teardown")
Cc: <redacted>
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 (local)
Signed-off-by: Chuck Lever <cel@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/nfsd/nfs4state.c | 16 +++++++++++++---
1 file changed, 13 insertions(+), 3 deletions(-)
--- a/fs/nfsd/nfs4state.c
+++ b/fs/nfsd/nfs4state.c
@@ -2338,14 +2338,24 @@ __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);