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

On Wed, May 17, 2017 at 02:59:39PM +0200, walter harms wrote:

Am 17.05.2017 14:35, schrieb Firo Yang:

quoted

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@google.com>
Signed-off-by: Firo Yang <redacted>
---
 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;

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

However, the 'dev' truly exists in this circumstance.

Thanks,
Firo

just my 2 cents,
re,
wh