netdev - Re: [PATCH] hdlcdrv: fix divide error bug if bitrate is 0

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Date:   Wed, 17 May 2017 14:59:39 +0200
From:   walter harms <wharms@....de>
To:     Firo Yang <firogm@...il.com>
CC:     t.sailer@...mni.ethz.ch, davem@...emloft.net,
        gregkh@...uxfoundation.org, linux-hams@...r.kernel.org,
        netdev@...r.kernel.org, dvyukov@...gle.com,
        syzkaller@...glegroups.com
Subject: Re: [PATCH] hdlcdrv: fix divide error bug if bitrate is 0



Am 17.05.2017 14:35, schrieb Firo Yang:
> The divisor s->par.bitrate will always be 0 until initialized by
> ndo_open() and hdlcdrv_open().
> 
> In order to fix this divide zero error, check whether the netdevice
> was opened by ndo_open() before performing divide.
> 
> Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
> Signed-off-by: Firo Yang <firogm@...il.com>
> ---
>  drivers/net/hamradio/hdlcdrv.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/hamradio/hdlcdrv.c b/drivers/net/hamradio/hdlcdrv.c
> index 8c3633c..3c783fd 100644
> --- a/drivers/net/hamradio/hdlcdrv.c
> +++ b/drivers/net/hamradio/hdlcdrv.c
> @@ -574,7 +574,7 @@ static int hdlcdrv_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
>  		break;		
>  
>  	case HDLCDRVCTL_CALIBRATE:
> -		if(!capable(CAP_SYS_RAWIO))
> +		if (!capable(CAP_SYS_RAWIO) || !netif_running(dev))
>  			return -EPERM;
>  		if (bi.data.calibrate > INT_MAX / s->par.bitrate)
>  			return -EINVAL;

I would still check for s->par.bitrate > 0 later changes may affect the setting of it
and it is much more obvious.

Also perhaps !netif_running(dev) should better return ENODEV.


just my 2 cents,
re,
 wh