drivers/net: fixed drivers that support netpoll use ndo_start_xmit()

The NETPOLL API requires that interrupts remain disabled in
netpoll_send_skb(). The use of spin_lock_irq() and spin_unlock_irq()
in the NETPOLL API callbacks causes the interrupts to get enabled and
can lead to kernel instability.

The solution is to use spin_lock_irqsave() and spin_unlock_restore()
to prevent the irqs from getting enabled while in netpoll_send_skb().

Call trace:
netpoll_send_skb()
{
   -> local_irq_save(flags)
     ---> dev->ndo_start_xmit(skb, dev)
         ---> spin_lock_irq()
         ---> spin_unlock_irq() *******here would enable the interrupt.
              ...
   -> local_irq_restore(flags)
}

Signed-off-by: Dongdong Deng <dongdong.deng@windriver.com>
Signed-off-by: Jason Wessel <jason.wessel@windriver.com>
Acked-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Acked-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/net/via-rhine.c b/drivers/net/via-rhine.c
index 88c30a58b4bd..934f7671650a 100644
--- a/drivers/net/via-rhine.c
+++ b/drivers/net/via-rhine.c
@@ -1218,6 +1218,7 @@ static int rhine_start_tx(struct sk_buff *skb, struct net_device *dev)
         struct rhine_private *rp = netdev_priv(dev);
         void __iomem *ioaddr = rp->base;
         unsigned entry;
+        unsigned long flags;
 
         /* Caution: the write order is important here, set the field
            with the "ownership" bits last. */
@@ -1261,7 +1262,7 @@ static int rhine_start_tx(struct sk_buff *skb, struct net_device *dev)
                 cpu_to_le32(TXDESC | (skb->len >= ETH_ZLEN ? skb->len : ETH_ZLEN));
 
         /* lock eth irq */
-        spin_lock_irq(&rp->lock);
+        spin_lock_irqsave(&rp->lock, flags);
         wmb();
         rp->tx_ring[entry].tx_status = cpu_to_le32(DescOwn);
         wmb();
@@ -1280,7 +1281,7 @@ static int rhine_start_tx(struct sk_buff *skb, struct net_device *dev)
 
         dev->trans_start = jiffies;
 
-        spin_unlock_irq(&rp->lock);
+        spin_unlock_irqrestore(&rp->lock, flags);
 
         if (debug > 4) {
                 printk(KERN_DEBUG "%s: Transmit frame #%d queued in slot %d.\n",