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authorPavel Emelyanov <xemul@openvz.org>2008-03-24 14:48:59 -0700
committerDavid S. Miller <davem@davemloft.net>2008-03-24 14:48:59 -0700
commitfa86d322d89995fef1bfb5cc768b89d8c22ea0d9 (patch)
treee657b8adc9ccd2e13b2e2276fab4733a273ded09 /net/ipv6/ndisc.c
parent8f3ea33a5078a09eba12bfe57424507809367756 (diff)
[NEIGH]: Fix race between pneigh deletion and ipv6's ndisc_recv_ns (v3).
Proxy neighbors do not have any reference counting, so any caller of pneigh_lookup (unless it's a netlink triggered add/del routine) should _not_ perform any actions on the found proxy entry. There's one exception from this rule - the ipv6's ndisc_recv_ns() uses found entry to check the flags for NTF_ROUTER. This creates a race between the ndisc and pneigh_delete - after the pneigh is returned to the caller, the nd_tbl.lock is dropped and the deleting procedure may proceed. One of the fixes would be to add a reference counting, but this problem exists for ndisc only. Besides such a patch would be too big for -rc4. So I propose to introduce a __pneigh_lookup() which is supposed to be called with the lock held and use it in ndisc code to check the flags on alive pneigh entry. Changes from v2: As David noticed, Exported the __pneigh_lookup() to ipv6 module. The checkpatch generates a warning on it, since the EXPORT_SYMBOL does not follow the symbol itself, but in this file all the exports come at the end, so I decided no to break this harmony. Changes from v1: Fixed comments from YOSHIFUJI - indentation of prototype in header and the pndisc_check_router() name - and a compilation fix, pointed by Daniel - the is_routed was (falsely) considered as uninitialized by gcc. Signed-off-by: Pavel Emelyanov <xemul@openvz.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv6/ndisc.c')
-rw-r--r--net/ipv6/ndisc.c22
1 files changed, 18 insertions, 4 deletions
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 51557c27a0cd..452a2ac4eec8 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -676,6 +676,20 @@ static void ndisc_solicit(struct neighbour *neigh, struct sk_buff *skb)
}
}
+static struct pneigh_entry *pndisc_check_router(struct net_device *dev,
+ struct in6_addr *addr, int *is_router)
+{
+ struct pneigh_entry *n;
+
+ read_lock_bh(&nd_tbl.lock);
+ n = __pneigh_lookup(&nd_tbl, &init_net, addr, dev);
+ if (n != NULL)
+ *is_router = (n->flags & NTF_ROUTER);
+ read_unlock_bh(&nd_tbl.lock);
+
+ return n;
+}
+
static void ndisc_recv_ns(struct sk_buff *skb)
{
struct nd_msg *msg = (struct nd_msg *)skb_transport_header(skb);
@@ -692,7 +706,7 @@ static void ndisc_recv_ns(struct sk_buff *skb)
struct pneigh_entry *pneigh = NULL;
int dad = ipv6_addr_any(saddr);
int inc;
- int is_router;
+ int is_router = 0;
if (ipv6_addr_is_multicast(&msg->target)) {
ND_PRINTK2(KERN_WARNING
@@ -790,8 +804,8 @@ static void ndisc_recv_ns(struct sk_buff *skb)
if (ipv6_chk_acast_addr(dev, &msg->target) ||
(idev->cnf.forwarding &&
(ipv6_devconf.proxy_ndp || idev->cnf.proxy_ndp) &&
- (pneigh = pneigh_lookup(&nd_tbl, &init_net,
- &msg->target, dev, 0)) != NULL)) {
+ (pneigh = pndisc_check_router(dev, &msg->target,
+ &is_router)) != NULL)) {
if (!(NEIGH_CB(skb)->flags & LOCALLY_ENQUEUED) &&
skb->pkt_type != PACKET_HOST &&
inc != 0 &&
@@ -812,7 +826,7 @@ static void ndisc_recv_ns(struct sk_buff *skb)
goto out;
}
- is_router = !!(pneigh ? pneigh->flags & NTF_ROUTER : idev->cnf.forwarding);
+ is_router = !!(pneigh ? is_router : idev->cnf.forwarding);
if (dad) {
struct in6_addr maddr;