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kernel/net/mctp/device.c
Jeremy Kerr 43f55f23f7 mctp: Add refcounts to mctp_dev 
Currently, we tie the struct mctp_dev lifetime to the underlying struct
net_device, and hold/put that device as a proxy for a separate mctp_dev
refcount. This works because we're not holding any references to the
mctp_dev that are different from the netdev lifetime.

In a future change we'll break that assumption though, as we'll need to
hold mctp_dev references in a workqueue, which might live past the
netdev unregister notification.

In order to support that, this change introduces a refcount on the
mctp_dev, currently taken by the net_device->mctp_ptr reference, and
released on netdev unregister events. We can then use this for future
references that might outlast the net device.

Signed-off-by: Jeremy Kerr <jk@codeconstruct.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2021-09-29 11:00:11 +01:00

433 lines
9.1 KiB
C
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// SPDX-License-Identifier: GPL-2.0
/*
* Management Component Transport Protocol (MCTP) - device implementation.
*
* Copyright (c) 2021 Code Construct
* Copyright (c) 2021 Google
*/
#include <linux/if_link.h>
#include <linux/mctp.h>
#include <linux/netdevice.h>
#include <linux/rcupdate.h>
#include <linux/rtnetlink.h>
#include <net/addrconf.h>
#include <net/netlink.h>
#include <net/mctp.h>
#include <net/mctpdevice.h>
#include <net/sock.h>
struct mctp_dump_cb {
int h;
int idx;
size_t a_idx;
};
/* unlocked: caller must hold rcu_read_lock */
struct mctp_dev *__mctp_dev_get(const struct net_device *dev)
{
return rcu_dereference(dev->mctp_ptr);
}
struct mctp_dev *mctp_dev_get_rtnl(const struct net_device *dev)
{
return rtnl_dereference(dev->mctp_ptr);
}
static int mctp_fill_addrinfo(struct sk_buff *skb, struct netlink_callback *cb,
struct mctp_dev *mdev, mctp_eid_t eid)
{
struct ifaddrmsg *hdr;
struct nlmsghdr *nlh;
nlh = nlmsg_put(skb, NETLINK_CB(cb->skb).portid, cb->nlh->nlmsg_seq,
RTM_NEWADDR, sizeof(*hdr), NLM_F_MULTI);
if (!nlh)
return -EMSGSIZE;
hdr = nlmsg_data(nlh);
hdr->ifa_family = AF_MCTP;
hdr->ifa_prefixlen = 0;
hdr->ifa_flags = 0;
hdr->ifa_scope = 0;
hdr->ifa_index = mdev->dev->ifindex;
if (nla_put_u8(skb, IFA_LOCAL, eid))
goto cancel;
if (nla_put_u8(skb, IFA_ADDRESS, eid))
goto cancel;
nlmsg_end(skb, nlh);
return 0;
cancel:
nlmsg_cancel(skb, nlh);
return -EMSGSIZE;
}
static int mctp_dump_dev_addrinfo(struct mctp_dev *mdev, struct sk_buff *skb,
struct netlink_callback *cb)
{
struct mctp_dump_cb *mcb = (void *)cb->ctx;
int rc = 0;
for (; mcb->a_idx < mdev->num_addrs; mcb->a_idx++) {
rc = mctp_fill_addrinfo(skb, cb, mdev, mdev->addrs[mcb->a_idx]);
if (rc < 0)
break;
}
return rc;
}
static int mctp_dump_addrinfo(struct sk_buff *skb, struct netlink_callback *cb)
{
struct mctp_dump_cb *mcb = (void *)cb->ctx;
struct net *net = sock_net(skb->sk);
struct hlist_head *head;
struct net_device *dev;
struct ifaddrmsg *hdr;
struct mctp_dev *mdev;
int ifindex;
int idx, rc;
hdr = nlmsg_data(cb->nlh);
// filter by ifindex if requested
ifindex = hdr->ifa_index;
rcu_read_lock();
for (; mcb->h < NETDEV_HASHENTRIES; mcb->h++, mcb->idx = 0) {
idx = 0;
head = &net->dev_index_head[mcb->h];
hlist_for_each_entry_rcu(dev, head, index_hlist) {
if (idx >= mcb->idx &&
(ifindex == 0 || ifindex == dev->ifindex)) {
mdev = __mctp_dev_get(dev);
if (mdev) {
rc = mctp_dump_dev_addrinfo(mdev,
skb, cb);
// Error indicates full buffer, this
// callback will get retried.
if (rc < 0)
goto out;
}
}
idx++;
// reset for next iteration
mcb->a_idx = 0;
}
}
out:
rcu_read_unlock();
mcb->idx = idx;
return skb->len;
}
static const struct nla_policy ifa_mctp_policy[IFA_MAX + 1] = {
[IFA_ADDRESS] = { .type = NLA_U8 },
[IFA_LOCAL] = { .type = NLA_U8 },
};
static int mctp_rtm_newaddr(struct sk_buff *skb, struct nlmsghdr *nlh,
struct netlink_ext_ack *extack)
{
struct net *net = sock_net(skb->sk);
struct nlattr *tb[IFA_MAX + 1];
struct net_device *dev;
struct mctp_addr *addr;
struct mctp_dev *mdev;
struct ifaddrmsg *ifm;
unsigned long flags;
u8 *tmp_addrs;
int rc;
rc = nlmsg_parse(nlh, sizeof(*ifm), tb, IFA_MAX, ifa_mctp_policy,
extack);
if (rc < 0)
return rc;
ifm = nlmsg_data(nlh);
if (tb[IFA_LOCAL])
addr = nla_data(tb[IFA_LOCAL]);
else if (tb[IFA_ADDRESS])
addr = nla_data(tb[IFA_ADDRESS]);
else
return -EINVAL;
/* find device */
dev = __dev_get_by_index(net, ifm->ifa_index);
if (!dev)
return -ENODEV;
mdev = mctp_dev_get_rtnl(dev);
if (!mdev)
return -ENODEV;
if (!mctp_address_ok(addr->s_addr))
return -EINVAL;
/* Prevent duplicates. Under RTNL so don't need to lock for reading */
if (memchr(mdev->addrs, addr->s_addr, mdev->num_addrs))
return -EEXIST;
tmp_addrs = kmalloc(mdev->num_addrs + 1, GFP_KERNEL);
if (!tmp_addrs)
return -ENOMEM;
memcpy(tmp_addrs, mdev->addrs, mdev->num_addrs);
tmp_addrs[mdev->num_addrs] = addr->s_addr;
/* Lock to write */
spin_lock_irqsave(&mdev->addrs_lock, flags);
mdev->num_addrs++;
swap(mdev->addrs, tmp_addrs);
spin_unlock_irqrestore(&mdev->addrs_lock, flags);
kfree(tmp_addrs);
mctp_route_add_local(mdev, addr->s_addr);
return 0;
}
static int mctp_rtm_deladdr(struct sk_buff *skb, struct nlmsghdr *nlh,
struct netlink_ext_ack *extack)
{
struct net *net = sock_net(skb->sk);
struct nlattr *tb[IFA_MAX + 1];
struct net_device *dev;
struct mctp_addr *addr;
struct mctp_dev *mdev;
struct ifaddrmsg *ifm;
unsigned long flags;
u8 *pos;
int rc;
rc = nlmsg_parse(nlh, sizeof(*ifm), tb, IFA_MAX, ifa_mctp_policy,
extack);
if (rc < 0)
return rc;
ifm = nlmsg_data(nlh);
if (tb[IFA_LOCAL])
addr = nla_data(tb[IFA_LOCAL]);
else if (tb[IFA_ADDRESS])
addr = nla_data(tb[IFA_ADDRESS]);
else
return -EINVAL;
/* find device */
dev = __dev_get_by_index(net, ifm->ifa_index);
if (!dev)
return -ENODEV;
mdev = mctp_dev_get_rtnl(dev);
if (!mdev)
return -ENODEV;
pos = memchr(mdev->addrs, addr->s_addr, mdev->num_addrs);
if (!pos)
return -ENOENT;
rc = mctp_route_remove_local(mdev, addr->s_addr);
// we can ignore -ENOENT in the case a route was already removed
if (rc < 0 && rc != -ENOENT)
return rc;
spin_lock_irqsave(&mdev->addrs_lock, flags);
memmove(pos, pos + 1, mdev->num_addrs - 1 - (pos - mdev->addrs));
mdev->num_addrs--;
spin_unlock_irqrestore(&mdev->addrs_lock, flags);
return 0;
}
void mctp_dev_hold(struct mctp_dev *mdev)
{
refcount_inc(&mdev->refs);
}
void mctp_dev_put(struct mctp_dev *mdev)
{
if (refcount_dec_and_test(&mdev->refs)) {
dev_put(mdev->dev);
kfree_rcu(mdev, rcu);
}
}
static struct mctp_dev *mctp_add_dev(struct net_device *dev)
{
struct mctp_dev *mdev;
ASSERT_RTNL();
mdev = kzalloc(sizeof(*mdev), GFP_KERNEL);
if (!mdev)
return ERR_PTR(-ENOMEM);
spin_lock_init(&mdev->addrs_lock);
mdev->net = mctp_default_net(dev_net(dev));
/* associate to net_device */
refcount_set(&mdev->refs, 1);
rcu_assign_pointer(dev->mctp_ptr, mdev);
dev_hold(dev);
mdev->dev = dev;
return mdev;
}
static int mctp_fill_link_af(struct sk_buff *skb,
const struct net_device *dev, u32 ext_filter_mask)
{
struct mctp_dev *mdev;
mdev = mctp_dev_get_rtnl(dev);
if (!mdev)
return -ENODATA;
if (nla_put_u32(skb, IFLA_MCTP_NET, mdev->net))
return -EMSGSIZE;
return 0;
}
static size_t mctp_get_link_af_size(const struct net_device *dev,
u32 ext_filter_mask)
{
struct mctp_dev *mdev;
unsigned int ret;
/* caller holds RCU */
mdev = __mctp_dev_get(dev);
if (!mdev)
return 0;
ret = nla_total_size(4); /* IFLA_MCTP_NET */
return ret;
}
static const struct nla_policy ifla_af_mctp_policy[IFLA_MCTP_MAX + 1] = {
[IFLA_MCTP_NET] = { .type = NLA_U32 },
};
static int mctp_set_link_af(struct net_device *dev, const struct nlattr *attr,
struct netlink_ext_ack *extack)
{
struct nlattr *tb[IFLA_MCTP_MAX + 1];
struct mctp_dev *mdev;
int rc;
rc = nla_parse_nested(tb, IFLA_MCTP_MAX, attr, ifla_af_mctp_policy,
NULL);
if (rc)
return rc;
mdev = mctp_dev_get_rtnl(dev);
if (!mdev)
return 0;
if (tb[IFLA_MCTP_NET])
WRITE_ONCE(mdev->net, nla_get_u32(tb[IFLA_MCTP_NET]));
return 0;
}
static void mctp_unregister(struct net_device *dev)
{
struct mctp_dev *mdev;
mdev = mctp_dev_get_rtnl(dev);
if (!mdev)
return;
RCU_INIT_POINTER(mdev->dev->mctp_ptr, NULL);
mctp_route_remove_dev(mdev);
mctp_neigh_remove_dev(mdev);
kfree(mdev->addrs);
mctp_dev_put(mdev);
}
static int mctp_register(struct net_device *dev)
{
struct mctp_dev *mdev;
/* Already registered? */
if (rtnl_dereference(dev->mctp_ptr))
return 0;
/* only register specific types (inc. NONE for TUN devices) */
if (!(dev->type == ARPHRD_MCTP ||
dev->type == ARPHRD_LOOPBACK ||
dev->type == ARPHRD_NONE)) {
return 0;
}
mdev = mctp_add_dev(dev);
if (IS_ERR(mdev))
return PTR_ERR(mdev);
return 0;
}
static int mctp_dev_notify(struct notifier_block *this, unsigned long event,
void *ptr)
{
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
int rc;
switch (event) {
case NETDEV_REGISTER:
rc = mctp_register(dev);
if (rc)
return notifier_from_errno(rc);
break;
case NETDEV_UNREGISTER:
mctp_unregister(dev);
break;
}
return NOTIFY_OK;
}
static struct rtnl_af_ops mctp_af_ops = {
.family = AF_MCTP,
.fill_link_af = mctp_fill_link_af,
.get_link_af_size = mctp_get_link_af_size,
.set_link_af = mctp_set_link_af,
};
static struct notifier_block mctp_dev_nb = {
.notifier_call = mctp_dev_notify,
.priority = ADDRCONF_NOTIFY_PRIORITY,
};
void __init mctp_device_init(void)
{
register_netdevice_notifier(&mctp_dev_nb);
rtnl_register_module(THIS_MODULE, PF_MCTP, RTM_GETADDR,
NULL, mctp_dump_addrinfo, 0);
rtnl_register_module(THIS_MODULE, PF_MCTP, RTM_NEWADDR,
mctp_rtm_newaddr, NULL, 0);
rtnl_register_module(THIS_MODULE, PF_MCTP, RTM_DELADDR,
mctp_rtm_deladdr, NULL, 0);
rtnl_af_register(&mctp_af_ops);
}
void __exit mctp_device_exit(void)
{
rtnl_af_unregister(&mctp_af_ops);
rtnl_unregister(PF_MCTP, RTM_DELADDR);
rtnl_unregister(PF_MCTP, RTM_NEWADDR);
rtnl_unregister(PF_MCTP, RTM_GETADDR);
unregister_netdevice_notifier(&mctp_dev_nb);
}
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