ipv6: addrconf: cleanup locking in ipv6_add_addr

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 3ad7d2468f79f ("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 3ad7d2468f79f 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 <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 60 insertions, 44 deletions

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 4603aa488f4f..a8d202b1b919 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -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);
 
@@ -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;
@@ -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;
         }
 
@@ -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);
 
@@ -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 {
@@ -1334,7 +1349,7 @@ retry:
 
         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);
@@ -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;
 
@@ -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;
@@ -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)) {
@@ -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;
@@ -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);