mkiss: ax_bump() locking fix

According to one of OOPSes reported by Jann softirq can break
while skb is prepared for netif_rx. The report isn't complete,
so the real reason of the later bug could be different, but
IMHO this locking break in ax_bump is unsafe and unnecessary.

Reported-and-tested-by: Jann Traschewski <jann@gmx.de>
Signed-off-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

1 files changed, 2 insertions, 3 deletions

diff --git a/drivers/net/hamradio/mkiss.c b/drivers/net/hamradio/mkiss.c
index cfcd15af501e..30c9b3b0d131 100644
--- a/drivers/net/hamradio/mkiss.c
+++ b/drivers/net/hamradio/mkiss.c
@@ -289,7 +289,6 @@ static void ax_bump(struct mkiss *ax)
                         *ax->rbuff &= ~0x20;
                 }
         }
-        spin_unlock_bh(&ax->buflock);
 
         count = ax->rcount;
 
@@ -297,17 +296,17 @@ static void ax_bump(struct mkiss *ax)
                 printk(KERN_ERR "mkiss: %s: memory squeeze, dropping packet.\n",
                        ax->dev->name);
                 ax->stats.rx_dropped++;
+                spin_unlock_bh(&ax->buflock);
                 return;
         }
 
-        spin_lock_bh(&ax->buflock);
         memcpy(skb_put(skb,count), ax->rbuff, count);
-        spin_unlock_bh(&ax->buflock);
         skb->protocol = ax25_type_trans(skb, ax->dev);
         netif_rx(skb);
         ax->dev->last_rx = jiffies;
         ax->stats.rx_packets++;
         ax->stats.rx_bytes += count;
+        spin_unlock_bh(&ax->buflock);
 }
 
 static void kiss_unesc(struct mkiss *ax, unsigned char s)