yam: avoid null pointer dereference error

On 27/03/13 17:46, David Miller wrote:
> 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.
>
Good point. How about the following..

On Wed, 2013-03-27 at 18:08 +0000, Colin Ian King wrote:
> On 27/03/13 17:46, David Miller wrote:
> > 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.
> >
> Good point. How about the following..

> From 564f111f196d9d7293e922a68ba973210d191129 Mon Sep 17 00:00:00 2001
> From: Colin Ian King <colin.king@canonical.com>
> Date: Wed, 27 Mar 2013 13:59:05 -0400
> Subject: [PATCH] yam: remove redundant null check on dev
> 
> yam_open has a redundant null check on null,  it will
> never be called with dev == NULL. Remove this redundant check.
> This also cleans up a smatch warning:
> 
> 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>

Reviewed-by: Ben Hutchings <bhutchings@solarflare.com>

(for what it's worth)

> ---
>  drivers/net/hamradio/yam.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/hamradio/yam.c b/drivers/net/hamradio/yam.c
> index 4cf8f10..b2d863f 100644
> --- a/drivers/net/hamradio/yam.c
> +++ b/drivers/net/hamradio/yam.c
> @@ -866,7 +866,7 @@ static int yam_open(struct net_device *dev)
>  
>         printk(KERN_INFO "Trying %s at iobase 0x%lx irq %u\n",
> dev->name, dev->base_addr, dev->irq);
>  
> -       if (!dev || !yp->bitrate)
> +       if (!yp->bitrate)
>                 return -ENXIO;
>         if (!dev->base_addr || dev->base_addr > 0x1000 - YAM_EXTENT ||
>                 dev->irq < 2 || dev->irq > 15) {

From: Ben Hutchings <bhutchings@solarflare.com>
Date: Wed, 27 Mar 2013 18:12:33 +0000

> On Wed, 2013-03-27 at 18:08 +0000, Colin Ian King wrote:
>> On 27/03/13 17:46, David Miller wrote:
>> > 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.
>> >
>> Good point. How about the following..
> 
>> From 564f111f196d9d7293e922a68ba973210d191129 Mon Sep 17 00:00:00 2001
>> From: Colin Ian King <colin.king@canonical.com>
>> Date: Wed, 27 Mar 2013 13:59:05 -0400
>> Subject: [PATCH] yam: remove redundant null check on dev
>> 
>> yam_open has a redundant null check on null,  it will
>> never be called with dev == NULL. Remove this redundant check.
>> This also cleans up a smatch warning:
>> 
>> 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>
> 
> Reviewed-by: Ben Hutchings <bhutchings@solarflare.com>

Colin, please formally resubmit this using a fresh mailing list
posting rather than as a reply in this thread.  Please incorporate
Ben's reviewed-by tag when doing so, thanks.
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