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ipv6: addrconf: cleanup locking in ipv6_add_addr
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ipv6_add_addr is called in process context with rtnl lock held
(e.g., manual config of an address) or during softirq processing
(e.g., autoconf and address from a router advertisement).

Currently, ipv6_add_addr calls rcu_read_lock_bh shortly after entry
and does not call unlock until exit, minus the call around the address
validator notifier. Similarly, addrconf_hash_lock is taken after the
validator notifier and held until exit. This forces the allocation of
inet6_ifaddr to always be atomic.

Refactor ipv6_add_addr as follows:
1. add an input boolean to discriminate the call path (process context
   or softirq). This new flag controls whether the alloc can be done
   with GFP_KERNEL or GFP_ATOMIC.

2. Move the rcu_read_lock_bh and unlock calls only around functions that
   do rcu updates.

3. Remove the in6_dev_hold and put added by 3ad7d24 ("Ipvlan should
   return an error when an address is already in use."). This was done
   presumably because rcu_read_unlock_bh needs to be called before calling
   the validator. Since rcu_read_lock is not needed before the validator
   runs revert the hold and put added by 3ad7d24 and only do the
   hold when setting ifp->idev.

4. move duplicate address check and insertion of new address in the global
   address hash into a helper. The helper is called after an ifa is
   allocated and filled in.

This allows the ifa for manually configured addresses to be done with
GFP_KERNEL and reduces the overall amount of time with rcu_read_lock held
and hash table spinlock held.

Signed-off-by: David Ahern <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
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@dsahern @davem330
dsahern authored and davem330 committed Oct 20, 2017
1 parent 6b1f8ed commit f3d9832
Showing 1 changed file with 60 additions and 44 deletions.
104 changes: 60 additions & 44 deletions net/ipv6/addrconf.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -957,18 +957,43 @@ static u32 inet6_addr_hash(const struct in6_addr *addr)
return hash_32(ipv6_addr_hash(addr), IN6_ADDR_HSIZE_SHIFT);
}

static int ipv6_add_addr_hash(struct net_device *dev, struct inet6_ifaddr *ifa)
{
unsigned int hash;
int err = 0;

spin_lock(&addrconf_hash_lock);

/* Ignore adding duplicate addresses on an interface */
if (ipv6_chk_same_addr(dev_net(dev), &ifa->addr, dev)) {
ADBG("ipv6_add_addr: already assigned\n");
err = -EEXIST;
goto out;
}

/* Add to big hash table */
hash = inet6_addr_hash(&ifa->addr);
hlist_add_head_rcu(&ifa->addr_lst, &inet6_addr_lst[hash]);

out:
spin_unlock(&addrconf_hash_lock);

return err;
}

/* On success it returns ifp with increased reference count */

static struct inet6_ifaddr *
ipv6_add_addr(struct inet6_dev *idev, const struct in6_addr *addr,
const struct in6_addr *peer_addr, int pfxlen,
int scope, u32 flags, u32 valid_lft, u32 prefered_lft)
int scope, u32 flags, u32 valid_lft, u32 prefered_lft,
bool can_block)
{
gfp_t gfp_flags = can_block ? GFP_KERNEL : GFP_ATOMIC;
struct net *net = dev_net(idev->dev);
struct inet6_ifaddr *ifa = NULL;
struct rt6_info *rt;
struct rt6_info *rt = NULL;
struct in6_validator_info i6vi;
unsigned int hash;
int err = 0;
int addr_type = ipv6_addr_type(addr);

Expand All @@ -978,42 +1003,24 @@ ipv6_add_addr(struct inet6_dev *idev, const struct in6_addr *addr,
addr_type & IPV6_ADDR_LOOPBACK))
return ERR_PTR(-EADDRNOTAVAIL);

rcu_read_lock_bh();

in6_dev_hold(idev);

if (idev->dead) {
err = -ENODEV; /*XXX*/
goto out2;
goto out;
}

if (idev->cnf.disable_ipv6) {
err = -EACCES;
goto out2;
goto out;
}

i6vi.i6vi_addr = *addr;
i6vi.i6vi_dev = idev;
rcu_read_unlock_bh();

err = inet6addr_validator_notifier_call_chain(NETDEV_UP, &i6vi);

rcu_read_lock_bh();
err = notifier_to_errno(err);
if (err)
goto out2;

spin_lock(&addrconf_hash_lock);

/* Ignore adding duplicate addresses on an interface */
if (ipv6_chk_same_addr(dev_net(idev->dev), addr, idev->dev)) {
ADBG("ipv6_add_addr: already assigned\n");
err = -EEXIST;
if (err < 0)
goto out;
}

ifa = kzalloc(sizeof(struct inet6_ifaddr), GFP_ATOMIC);

ifa = kzalloc(sizeof(*ifa), gfp_flags);
if (!ifa) {
ADBG("ipv6_add_addr: malloc failed\n");
err = -ENOBUFS;
Expand All @@ -1023,6 +1030,7 @@ ipv6_add_addr(struct inet6_dev *idev, const struct in6_addr *addr,
rt = addrconf_dst_alloc(idev, addr, false);
if (IS_ERR(rt)) {
err = PTR_ERR(rt);
rt = NULL;
goto out;
}

Expand Down Expand Up @@ -1053,16 +1061,21 @@ ipv6_add_addr(struct inet6_dev *idev, const struct in6_addr *addr,
ifa->rt = rt;

ifa->idev = idev;
in6_dev_hold(idev);

/* For caller */
refcount_set(&ifa->refcnt, 1);

/* Add to big hash table */
hash = inet6_addr_hash(addr);
rcu_read_lock_bh();

hlist_add_head_rcu(&ifa->addr_lst, &inet6_addr_lst[hash]);
spin_unlock(&addrconf_hash_lock);
err = ipv6_add_addr_hash(idev->dev, ifa);
if (err < 0) {
rcu_read_unlock_bh();
goto out;
}

write_lock(&idev->lock);

/* Add to inet6_dev unicast addr list. */
ipv6_link_dev_addr(idev, ifa);

Expand All @@ -1073,21 +1086,23 @@ ipv6_add_addr(struct inet6_dev *idev, const struct in6_addr *addr,

in6_ifa_hold(ifa);
write_unlock(&idev->lock);
out2:

rcu_read_unlock_bh();

if (likely(err == 0))
inet6addr_notifier_call_chain(NETDEV_UP, ifa);
else {
kfree(ifa);
in6_dev_put(idev);
inet6addr_notifier_call_chain(NETDEV_UP, ifa);
out:
if (unlikely(err < 0)) {
if (rt)
ip6_rt_put(rt);
if (ifa) {
if (ifa->idev)
in6_dev_put(ifa->idev);
kfree(ifa);
}
ifa = ERR_PTR(err);
}

return ifa;
out:
spin_unlock(&addrconf_hash_lock);
goto out2;
}

enum cleanup_prefix_rt_t {
Expand Down Expand Up @@ -1334,7 +1349,7 @@ static int ipv6_create_tempaddr(struct inet6_ifaddr *ifp, struct inet6_ifaddr *i

ift = ipv6_add_addr(idev, &addr, NULL, tmp_plen,
ipv6_addr_scope(&addr), addr_flags,
tmp_valid_lft, tmp_prefered_lft);
tmp_valid_lft, tmp_prefered_lft, true);
if (IS_ERR(ift)) {
in6_ifa_put(ifp);
in6_dev_put(idev);
Expand Down Expand Up @@ -2018,7 +2033,7 @@ void addrconf_dad_failure(struct inet6_ifaddr *ifp)

ifp2 = ipv6_add_addr(idev, &new_addr, NULL, pfxlen,
scope, flags, valid_lft,
preferred_lft);
preferred_lft, false);
if (IS_ERR(ifp2))
goto lock_errdad;

Expand Down Expand Up @@ -2476,7 +2491,7 @@ int addrconf_prefix_rcv_add_addr(struct net *net, struct net_device *dev,
pinfo->prefix_len,
addr_type&IPV6_ADDR_SCOPE_MASK,
addr_flags, valid_lft,
prefered_lft);
prefered_lft, false);

if (IS_ERR_OR_NULL(ifp))
return -1;
Expand Down Expand Up @@ -2845,7 +2860,7 @@ static int inet6_addr_add(struct net *net, int ifindex,
}

ifp = ipv6_add_addr(idev, pfx, peer_pfx, plen, scope, ifa_flags,
valid_lft, prefered_lft);
valid_lft, prefered_lft, true);

if (!IS_ERR(ifp)) {
if (!(ifa_flags & IFA_F_NOPREFIXROUTE)) {
Expand Down Expand Up @@ -2960,7 +2975,8 @@ static void add_addr(struct inet6_dev *idev, const struct in6_addr *addr,

ifp = ipv6_add_addr(idev, addr, NULL, plen,
scope, IFA_F_PERMANENT,
INFINITY_LIFE_TIME, INFINITY_LIFE_TIME);
INFINITY_LIFE_TIME, INFINITY_LIFE_TIME,
true);
if (!IS_ERR(ifp)) {
spin_lock_bh(&ifp->lock);
ifp->flags &= ~IFA_F_TENTATIVE;
Expand Down Expand Up @@ -3060,7 +3076,7 @@ void addrconf_add_linklocal(struct inet6_dev *idev,
#endif

ifp = ipv6_add_addr(idev, addr, NULL, 64, IFA_LINK, addr_flags,
INFINITY_LIFE_TIME, INFINITY_LIFE_TIME);
INFINITY_LIFE_TIME, INFINITY_LIFE_TIME, true);
if (!IS_ERR(ifp)) {
addrconf_prefix_route(&ifp->addr, ifp->prefix_len, idev->dev, 0, 0);
addrconf_dad_start(ifp);
Expand Down

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