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netpoll: Disable IRQ around RCU dereference in netpoll_rx

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We cannot use rcu_dereference_bh safely in netpoll_rx as we may
be called with IRQs disabled.  We could however simply disable
IRQs as that too causes BH to be disabled and is safe in either
case.

Thanks to John Linville for discovering this bug and providing
a patch.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Herbert Xu 2010-09-17 16:55:03 -07:00 committed by David S. Miller
parent 4bdab43323
commit f0f9deae9e
1 changed files with 4 additions and 4 deletions
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8
include/linux/netpoll.h
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@ -63,20 +63,20 @@ static inline bool netpoll_rx(struct sk_buff *skb)
unsigned long flags;
bool ret = false;
rcu_read_lock_bh();
local_irq_save(flags);
npinfo = rcu_dereference_bh(skb->dev->npinfo);
if (!npinfo || (list_empty(&npinfo->rx_np) && !npinfo->rx_flags))
goto out;
spin_lock_irqsave(&npinfo->rx_lock, flags);
spin_lock(&npinfo->rx_lock);
/* check rx_flags again with the lock held */
if (npinfo->rx_flags && __netpoll_rx(skb))
ret = true;
spin_unlock_irqrestore(&npinfo->rx_lock, flags);
spin_unlock(&npinfo->rx_lock);
out:
rcu_read_unlock_bh();
local_irq_restore(flags);
return ret;
}