yam: avoid null pointer dereference error

From: Colin Ian King <colin.king@canonical.com>

yam_open checks if dev is null, however, before that check it
accesses some of the fields from dev in a proceeding printk which
will cause a null pointer dereference error if dev is nul. Move
the printk to after the null check.

Smatch analysis:

drivers/net/hamradio/yam.c:869 yam_open() warn: variable
  dereferenced before check 'dev' (see line 867)

Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/net/hamradio/yam.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

On Wed, 2013-03-27 at 11:19 +0000, Colin King wrote:
> From: Colin Ian King <colin.king@canonical.com>
> 
> yam_open checks if dev is null, however, before that check it
> accesses some of the fields from dev in a proceeding printk which
> will cause a null pointer dereference error if dev is nul. Move
> the printk to after the null check.

This function will never be called with dev == NULL.

Ben.

> Smatch analysis:
> 
> drivers/net/hamradio/yam.c:869 yam_open() warn: variable
>   dereferenced before check 'dev' (see line 867)
> 
> Signed-off-by: Colin Ian King <colin.king@canonical.com>
> ---
>  drivers/net/hamradio/yam.c |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/net/hamradio/yam.c b/drivers/net/hamradio/yam.c
> index 4cf8f10..e021e51 100644
> --- a/drivers/net/hamradio/yam.c
> +++ b/drivers/net/hamradio/yam.c
> @@ -864,10 +864,11 @@ static int yam_open(struct net_device *dev)
>  	int i;
>  	int ret=0;
>  
> -	printk(KERN_INFO "Trying %s at iobase 0x%lx irq %u\n", dev->name, dev->base_addr, dev->irq);
> -
>  	if (!dev || !yp->bitrate)
>  		return -ENXIO;
> +
> +	printk(KERN_INFO "Trying %s at iobase 0x%lx irq %u\n", dev->name, dev->base_addr, dev->irq);
> +
>  	if (!dev->base_addr || dev->base_addr > 0x1000 - YAM_EXTENT ||
>  		dev->irq < 2 || dev->irq > 15) {
>  		return -ENXIO;

From: Ben Hutchings <bhutchings@solarflare.com>
Date: Wed, 27 Mar 2013 17:44:17 +0000

> On Wed, 2013-03-27 at 11:19 +0000, Colin King wrote:
>> From: Colin Ian King <colin.king@canonical.com>
>> 
>> yam_open checks if dev is null, however, before that check it
>> accesses some of the fields from dev in a proceeding printk which
>> will cause a null pointer dereference error if dev is nul. Move
>> the printk to after the null check.
> 
> This function will never be called with dev == NULL.

Then let's remove at least that part of the check.
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