[PATCH v2] hdlcdrv: fix divide error bug if bitrate is 0

[PATCH v2] hdlcdrv: fix divide error bug if bitrate is 0

[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.And we also check the the
value of bitrate in case of bad setting of it.

Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Firo Yang <firogm@gmail.com>
---
v1->v2:
	Change Reported-by to Andrey Konovalov.
	Send it to original report thread.

v0->v1:
        Reviewed by walter harms <wharms@bfs.de>.
        Return ENODEV instead of EPERM if !netif_running(dev)
        Check if s->par.bitrate > 0.
 drivers/net/hamradio/hdlcdrv.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/net/hamradio/hdlcdrv.c b/drivers/net/hamradio/hdlcdrv.c
index 8c3633c..b0f417f 100644
--- a/drivers/net/hamradio/hdlcdrv.c
+++ b/drivers/net/hamradio/hdlcdrv.c
@@ -576,6 +576,10 @@ static int hdlcdrv_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
 	case HDLCDRVCTL_CALIBRATE:
 		if(!capable(CAP_SYS_RAWIO))
 			return -EPERM;
+		if (!netif_running(dev))
+			return -ENODEV;
+		if (!(s->par.bitrate > 0))
+			return -EINVAL;
 		if (bi.data.calibrate > INT_MAX / s->par.bitrate)
 			return -EINVAL;
 		s->hdlctx.calibrate = bi.data.calibrate * s->par.bitrate / 16;
-- 
2.9.4

Re: [PATCH v2] hdlcdrv: fix divide error bug if bitrate is 0

[David Miller]

From: Firo Yang <firogm@gmail.com>
Date: Fri, 19 May 2017 21:21:46 +0800

> @@ -576,6 +576,10 @@ static int hdlcdrv_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
>  	case HDLCDRVCTL_CALIBRATE:
>  		if(!capable(CAP_SYS_RAWIO))
>  			return -EPERM;
> +		if (!netif_running(dev))
> +			return -ENODEV;
> +		if (!(s->par.bitrate > 0))
> +			return -EINVAL;

This test is so un-canonical and convoluted.

Please use something more straightforward.  I really think Alan
Cox's patch handled this more cleanly.  Make the test something
like "if (x <= 0) return -EINVAL;".

I also am not convinced about the netif_running() test and at
best it is a separate change from this divide by zero bug fix
so belongs in a separate patch.

Thank you.

[PATCH v3] hdlcdrv: Fix divide by zero in hdlcdrv_ioctl

[Firo Yang]

syszkaller fuzzer triggered a divide by zero, when set calibration
through ioctl().

To fix it, test 'bitrate' if it is negative or 0, just return -EINVAL.

Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Firo Yang <firogm@gmail.com>
---
v2->v3:
	Just fix divide error and remove netif_running() test.
	Refine the testing code as David Miller suggested.

v1->v2:
        Change Reported-by to Andrey Konovalov.
        Send it to original report thread.

v0->v1:
        Reviewed by walter harms <wharms@bfs.de>.
        Return ENODEV instead of EPERM if !netif_running(dev)
        Check if s->par.bitrate > 0.
 drivers/net/hamradio/hdlcdrv.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/hamradio/hdlcdrv.c b/drivers/net/hamradio/hdlcdrv.c
index 8c3633c..97e3bc6 100644
--- a/drivers/net/hamradio/hdlcdrv.c
+++ b/drivers/net/hamradio/hdlcdrv.c
@@ -576,6 +576,8 @@ static int hdlcdrv_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
 	case HDLCDRVCTL_CALIBRATE:
 		if(!capable(CAP_SYS_RAWIO))
 			return -EPERM;
+		if (s->par.bitrate <= 0)
+			return -EINVAL;
 		if (bi.data.calibrate > INT_MAX / s->par.bitrate)
 			return -EINVAL;
 		s->hdlctx.calibrate = bi.data.calibrate * s->par.bitrate / 16;
-- 
2.9.4

Re: [PATCH v3] hdlcdrv: Fix divide by zero in hdlcdrv_ioctl

[David Miller]

From: Firo Yang <firogm@gmail.com>
Date: Fri, 26 May 2017 22:37:38 +0800

> syszkaller fuzzer triggered a divide by zero, when set calibration
> through ioctl().
> 
> To fix it, test 'bitrate' if it is negative or 0, just return -EINVAL.
> 
> Reported-by: Andrey Konovalov <andreyknvl@google.com>
> Signed-off-by: Firo Yang <firogm@gmail.com>

Applied, thank you.