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Subject[2/3] [NEIGH] Fix add_timer race in neigh_add_timer
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[NEIGH] Fix add_timer race in neigh_add_timer

neigh_add_timer cannot use add_timer unconditionally. The reason is that
by the time it has obtained the write lock someone else (e.g., neigh_update)
could have already added a new timer.

So it should only use mod_timer and deal with its return value accordingly.

This bug would have led to rare neighbour cache entry leaks.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
--
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txtdiff --git a/net/core/neighbour.c b/net/core/neighbour.c
--- a/net/core/neighbour.c
+++ b/net/core/neighbour.c
@@ -816,10 +816,10 @@ static void neigh_timer_handler(unsigned
}

if (neigh->nud_state & NUD_IN_TIMER) {
- neigh_hold(neigh);
if (time_before(next, jiffies + HZ/2))
next = jiffies + HZ/2;
- neigh_add_timer(neigh, next);
+ if (!mod_timer(&neigh->timer, next))
+ neigh_hold(neigh);
}
if (neigh->nud_state & (NUD_INCOMPLETE | NUD_PROBE)) {
struct sk_buff *skb = skb_peek(&neigh->arp_queue);
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