[PATCH AUTOSEL for 4.4 097/167] hdlcdrv: Fix divide by zero in hdlcdrv_ioctl

[Sasha Levin]

From: Firo Yang <fir...@gmail.com>

[ Upstream commit fb3ce90b7d7761b6f7f28f0ff5c456ef6b5229a1 ]

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 <andreyk...@google.com>
Signed-off-by: Firo Yang <fir...@gmail.com>
Signed-off-by: David S. Miller <da...@davemloft.net>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
---
 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 49fe59b180a8..a75ce9051a7f 100644
--- a/drivers/net/hamradio/hdlcdrv.c
+++ b/drivers/net/hamradio/hdlcdrv.c
@@ -574,6 +574,8 @@ 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;
-- 
2.14.1