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Message-ID: <20170518032930.GB13146@snow.wrs.com> Date: Thu, 18 May 2017 11:29:30 +0800 From: Firo Yang <firogm@...il.com> To: walter harms <wharms@....de> Cc: linux-hams@...r.kernel.org, netdev@...r.kernel.org Subject: Re: [PATCH] hdlcdrv: fix divide error bug if bitrate is 0 On Wed, May 17, 2017 at 06:08:11PM +0200, walter harms wrote: > > >Am 17.05.2017 15:42, schrieb Firo Yang: >> On Wed, May 17, 2017 at 02:59:39PM +0200, walter harms wrote: >>> >>> >>> 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. >> >> I think 0 is not valid value for bitrate, so we should check it in >> other places, like what ser12_open() did: >> 429 if (bc->baud < 300 || bc->baud > 4800) { >> 430 printk(KERN_INFO "baycom_ser_fdx: invalid baudrate " >> 431 "(300...4800)\n"); >> 432 return -EINVAL; >> 433 } >> ... >> 440 bc->hdrv.par.bitrate = bc->baud; > > >I do not want to say you change is not valid but i have learned that it is better to >have an obvious check that to rely on hidden knowledge. I agree with this. > > >> >>> >>> Also perhaps !netif_running(dev) should better return ENODEV. >> >> However, the 'dev' truly exists in this circumstance. >> > >yes and i do not feel good with that but "no permission" will lead >any enduser into a search for user rights. Indeed, ENODEV is more informative to enduser. I will send a update patch. Thanks, Firo > > > >re, > wh > > >> Thanks, >> Firo >> >>> >>> >>> just my 2 cents, >>> re, >>> wh >>>
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