Subject: Re: [CORRECTION][PATCH] Fix a potential NULL pointer dereference in uli526x_interrupt() in drivers/net/tulip/uli526x.c

From: Andrew Morton <[email-masked]>
Date: Thu, 13 Sep 2007 02:03:46 -0700

On Tue, 04 Sep 2007 16:14:06 +0800 Micah Gruber <[email-masked]> wrote:

> This patch fixes a potential null dereference bug where we dereference dev before a null check. This patch simply moves the dereferencing after the null check.
> 
> Signed-off-by: Micah Gruber <[email-masked]>
> ---
> 
> --- a/drivers/net/tulip/uli526x.c
> +++ b/drivers/net/tulip/uli526x.c
> @@ -663,7 +663,7 @@
>  {
>  	struct net_device *dev = dev_id;
>  	struct uli526x_board_info *db = netdev_priv(dev);
> -	unsigned long ioaddr = dev->base_addr;
> +	unsigned long ioaddr;
>  	unsigned long flags;
>  
>  	if (!dev) {
> @@ -671,6 +671,8 @@
>  		return IRQ_NONE;
>  	}
>  
> +	ioaddr = dev->base_addr;
> +
>  	spin_lock_irqsave(&db->lock, flags);
>  	outl(0, ioaddr + DCR7);
> 

I suspect the fix we want is:

--- a/drivers/net/tulip/uli526x.c~fix-a-potential-null-pointer-dereference-in-uli526x_interrupt
+++ a/drivers/net/tulip/uli526x.c
@@ -666,11 +666,6 @@ static irqreturn_t uli526x_interrupt(int
 	unsigned long ioaddr = dev->base_addr;
 	unsigned long flags;
 
-	if (!dev) {
-		ULI526X_DBUG(1, "uli526x_interrupt() without DEVICE arg", 0);
-		return IRQ_NONE;
-	}
-
 	spin_lock_irqsave(&db->lock, flags);
 	outl(0, ioaddr + DCR7);
 
_