netdev - [PATCH][AX25] mkiss: ax

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Message-ID: <20080213111758.GA2867@ff.dom.local>
Date:	Wed, 13 Feb 2008 11:17:58 +0000
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Jeff Garzik <jeff@...zik.org>, David Miller <davem@...emloft.net>
Cc:	Jann Traschewski <jann@....de>, Ralf Baechle <ralf@...ux-mips.org>,
	netdev@...r.kernel.org
Subject: [PATCH][AX25] mkiss: ax_bump() locking fix

Hi,

This is unchanged patch previously sent here for testing.
I think it should be applied.

Thanks,
Jarek P.

---------------->

Subject: [PATCH][AX25] 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@....de>
Signed-off-by: Jarek Poplawski <jarkao2@...il.com>

---

 drivers/net/hamradio/mkiss.c |    5 ++---
 1 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/net/hamradio/mkiss.c b/drivers/net/hamradio/mkiss.c
index cfcd15a..30c9b3b 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)
--
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