Re: [PATCH] Hamradio: Fix a NULL pointer dereference in net/hamradio/mkiss.c

From: Alexey Dobriyan
Date: Thu Mar 16 2006 - 03:21:32 EST


On Thu, Mar 16, 2006 at 03:07:37PM +0800, Eugene Teo wrote:
> Pointer ax is dereferenced before NULL check.
>
> Coverity bug #817

> --- linux-2.6/drivers/net/hamradio/mkiss.c
> +++ linux-2.6/drivers/net/hamradio/mkiss.c
> @@ -845,13 +845,15 @@ static int mkiss_ioctl(struct tty_struct
> unsigned int cmd, unsigned long arg)
> {
> struct mkiss *ax = mkiss_get(tty);
> - struct net_device *dev = ax->dev;
> + struct net_device *dev;
> unsigned int tmp, err;
>
> /* First make sure we're connected. */
> if (ax == NULL)
> return -ENXIO;
>
> + dev = ax->dev;
> +

Actual codepath, please... valid "ax" is plonked into ->disc_data in
mkiss_open().

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