Commit 6fb9974f authored by Herbert Xu's avatar Herbert Xu

[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: default avatarHerbert Xu <>
parent 20375502
......@@ -816,10 +816,10 @@ static void neigh_timer_handler(unsigned long arg)
if (neigh->nud_state & NUD_IN_TIMER) {
if (time_before(next, jiffies + HZ/2))
next = jiffies + HZ/2;
neigh_add_timer(neigh, next);
if (!mod_timer(&neigh->timer, next))
if (neigh->nud_state & (NUD_INCOMPLETE | NUD_PROBE)) {
struct sk_buff *skb = skb_peek(&neigh->arp_queue);
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