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net: fix possible store tearing in neigh_periodic_work() 

While looking at a related syzbot report involving neigh_periodic_work(),
I found that I forgot to add an annotation when deleting an
RCU protected item from a list.

Readers use rcu_deference(*np), we need to use either
rcu_assign_pointer() or WRITE_ONCE() on writer side
to prevent store tearing.

I use rcu_assign_pointer() to have lockdep support,
this was the choice made in neigh_flush_dev().

Fixes: 767e97e1e0 ("neigh: RCU conversion of struct neighbour")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2023-09-21 08:46:26 +00:00 committed by David S. Miller
parent c15cd642d4
commit 25563b581b
1 changed files with 3 additions and 1 deletions
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4
net/core/neighbour.c
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@ -988,7 +988,9 @@ static void neigh_periodic_work(struct work_struct *work)
(state == NUD_FAILED ||
!time_in_range_open(jiffies, n->used,
n->used + NEIGH_VAR(n->parms, GC_STALETIME)))) {
*np = n->next;
rcu_assign_pointer(*np,
rcu_dereference_protected(n->next,
lockdep_is_held(&tbl->lock)));
neigh_mark_dead(n);
write_unlock(&n->lock);
neigh_cleanup_and_release(n);