// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2024 Mike Snitzer <[email protected]>
* Copyright (C) 2024 NeilBrown <[email protected]>
*/
#include <linux/module.h>
#include <linux/rculist.h>
#include <linux/nfslocalio.h>
#include <net/netns/generic.h>
MODULE_LICENSE("GPL");
MODULE_DESCRIPTION("NFS localio protocol bypass support");
static DEFINE_SPINLOCK(nfs_uuid_lock);
/*
* Global list of nfs_uuid_t instances
* that is protected by nfs_uuid_lock.
*/
static LIST_HEAD(nfs_uuids);
void nfs_uuid_begin(nfs_uuid_t *nfs_uuid)
{
nfs_uuid->net = NULL;
nfs_uuid->dom = NULL;
uuid_gen(&nfs_uuid->uuid);
spin_lock(&nfs_uuid_lock);
list_add_tail_rcu(&nfs_uuid->list, &nfs_uuids);
spin_unlock(&nfs_uuid_lock);
}
EXPORT_SYMBOL_GPL(nfs_uuid_begin);
void nfs_uuid_end(nfs_uuid_t *nfs_uuid)
{
if (nfs_uuid->net == NULL) {
spin_lock(&nfs_uuid_lock);
list_del_init(&nfs_uuid->list);
spin_unlock(&nfs_uuid_lock);
}
}
EXPORT_SYMBOL_GPL(nfs_uuid_end);
static nfs_uuid_t * nfs_uuid_lookup_locked(const uuid_t *uuid)
{
nfs_uuid_t *nfs_uuid;
list_for_each_entry(nfs_uuid, &nfs_uuids, list)
if (uuid_equal(&nfs_uuid->uuid, uuid))
return nfs_uuid;
return NULL;
}
static struct module *nfsd_mod;
void nfs_uuid_is_local(const uuid_t *uuid, struct list_head *list,
struct net *net, struct auth_domain *dom,
struct module *mod)
{
nfs_uuid_t *nfs_uuid;
spin_lock(&nfs_uuid_lock);
nfs_uuid = nfs_uuid_lookup_locked(uuid);
if (nfs_uuid) {
kref_get(&dom->ref);
nfs_uuid->dom = dom;
/*
* We don't hold a ref on the net, but instead put
* ourselves on a list so the net pointer can be
* invalidated.
*/
list_move(&nfs_uuid->list, list);
rcu_assign_pointer(nfs_uuid->net, net);
__module_get(mod);
nfsd_mod = mod;
}
spin_unlock(&nfs_uuid_lock);
}
EXPORT_SYMBOL_GPL(nfs_uuid_is_local);
static void nfs_uuid_put_locked(nfs_uuid_t *nfs_uuid)
{
if (nfs_uuid->net) {
module_put(nfsd_mod);
nfs_uuid->net = NULL;
}
if (nfs_uuid->dom) {
auth_domain_put(nfs_uuid->dom);
nfs_uuid->dom = NULL;
}
list_del_init(&nfs_uuid->list);
}
void nfs_uuid_invalidate_clients(struct list_head *list)
{
nfs_uuid_t *nfs_uuid, *tmp;
spin_lock(&nfs_uuid_lock);
list_for_each_entry_safe(nfs_uuid, tmp, list, list)
nfs_uuid_put_locked(nfs_uuid);
spin_unlock(&nfs_uuid_lock);
}
EXPORT_SYMBOL_GPL(nfs_uuid_invalidate_clients);
void nfs_uuid_invalidate_one_client(nfs_uuid_t *nfs_uuid)
{
if (nfs_uuid->net) {
spin_lock(&nfs_uuid_lock);
nfs_uuid_put_locked(nfs_uuid);
spin_unlock(&nfs_uuid_lock);
}
}
EXPORT_SYMBOL_GPL(nfs_uuid_invalidate_one_client);
struct nfsd_file *nfs_open_local_fh(nfs_uuid_t *uuid,
struct rpc_clnt *rpc_clnt, const struct cred *cred,
const struct nfs_fh *nfs_fh, const fmode_t fmode)
{
struct net *net;
struct nfsd_file *localio;
/*
* Not running in nfsd context, so must safely get reference on nfsd_serv.
* But the server may already be shutting down, if so disallow new localio.
* uuid->net is NOT a counted reference, but rcu_read_lock() ensures that
* if uuid->net is not NULL, then calling nfsd_serv_try_get() is safe
* and if it succeeds we will have an implied reference to the net.
*
* Otherwise NFS may not have ref on NFSD and therefore cannot safely
* make 'nfs_to' calls.
*/
rcu_read_lock();
net = rcu_dereference(uuid->net);
if (!net || !nfs_to->nfsd_serv_try_get(net)) {
rcu_read_unlock();
return ERR_PTR(-ENXIO);
}
rcu_read_unlock();
/* We have an implied reference to net thanks to nfsd_serv_try_get */
localio = nfs_to->nfsd_open_local_fh(net, uuid->dom, rpc_clnt,
cred, nfs_fh, fmode);
if (IS_ERR(localio))
nfs_to->nfsd_serv_put(net);
return localio;
}
EXPORT_SYMBOL_GPL(nfs_open_local_fh);
/*
* The NFS LOCALIO code needs to call into NFSD using various symbols,
* but cannot be statically linked, because that will make the NFS
* module always depend on the NFSD module.
*
* 'nfs_to' provides NFS access to NFSD functions needed for LOCALIO,
* its lifetime is tightly coupled to the NFSD module and will always
* be available to NFS LOCALIO because any successful client<->server
* LOCALIO handshake results in a reference on the NFSD module (above),
* so NFS implicitly holds a reference to the NFSD module and its
* functions in the 'nfs_to' nfsd_localio_operations cannot disappear.
*
* If the last NFS client using LOCALIO disconnects (and its reference
* on NFSD dropped) then NFSD could be unloaded, resulting in 'nfs_to'
* functions being invalid pointers. But if NFSD isn't loaded then NFS
* will not be able to handshake with NFSD and will have no cause to
* try to call 'nfs_to' function pointers. If/when NFSD is reloaded it
* will reinitialize the 'nfs_to' function pointers and make LOCALIO
* possible.
*/
const struct nfsd_localio_operations *nfs_to;
EXPORT_SYMBOL_GPL(nfs_to);
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