Commit 2c51a97f authored by Julian Anastasov's avatar Julian Anastasov Committed by David S. Miller
Browse files

neigh: do not modify unlinked entries

The lockless lookups can return entry that is unlinked.
Sometimes they get reference before last neigh_cleanup_and_release,
sometimes they do not need reference. Later, any
modification attempts may result in the following problems:

1. entry is not destroyed immediately because neigh_update
can start the timer for dead entry, eg. on change to NUD_REACHABLE
state. As result, entry lives for some time but is invisible
and out of control.

2. __neigh_event_send can run in parallel with neigh_destroy
while refcnt=0 but if timer is started and expired refcnt can
reach 0 for second time leading to second neigh_destroy and
possible crash.

Thanks to Eric Dumazet and Ying Xue for their work and analyze
on the __neigh_event_send change.

Fixes: 767e97e1 ("neigh: RCU conversion of struct neighbour")
Fixes: a263b309 ("ipv4: Make neigh lookups directly in output packet path.")
Fixes: 6fd6ce20

 ("ipv6: Do not depend on rt->n in ip6_finish_output2().")
Cc: Eric Dumazet <>
Cc: Ying Xue <>
Signed-off-by: default avatarJulian Anastasov <>
Acked-by: default avatarEric Dumazet <>
Signed-off-by: default avatarDavid S. Miller <>
parent f98f4514
......@@ -957,6 +957,8 @@ int __neigh_event_send(struct neighbour *neigh, struct sk_buff *skb)
rc = 0;
if (neigh->nud_state & (NUD_CONNECTED | NUD_DELAY | NUD_PROBE))
goto out_unlock_bh;
if (neigh->dead)
goto out_dead;
if (!(neigh->nud_state & (NUD_STALE | NUD_INCOMPLETE))) {
if (NEIGH_VAR(neigh->parms, MCAST_PROBES) +
......@@ -1013,6 +1015,13 @@ out_unlock_bh:
return rc;
if (neigh->nud_state & NUD_STALE)
goto out_unlock_bh;
return 1;
......@@ -1076,6 +1085,8 @@ int neigh_update(struct neighbour *neigh, const u8 *lladdr, u8 new,
if (!(flags & NEIGH_UPDATE_F_ADMIN) &&
goto out;
if (neigh->dead)
goto out;
if (!(new & NUD_VALID)) {
......@@ -1225,6 +1236,8 @@ EXPORT_SYMBOL(neigh_update);
void __neigh_set_probe_once(struct neighbour *neigh)
if (neigh->dead)
neigh->updated = jiffies;
if (!(neigh->nud_state & NUD_FAILED))
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