Re: drivers/net/hamradio: divide error in hdlcdrv_ioctl

From	Andrey Konovalov <andreyknvl@google.com>
Newsgroups	linux.kernel
Subject	Re: drivers/net/hamradio: divide error in hdlcdrv_ioctl
Date	2017-05-19 02:30 +0200
Message-ID	<tIDXQ-2u0-7@gated-at.bofh.it> (permalink)
References	<tHMgN-7cr-3@gated-at.bofh.it> <tIdqG-7Gg-23@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Wed, May 17, 2017 at 10:07 PM, Alan Cox <gnomes@lxorguk.ukuu.org.uk> wrote:
> On Tue, 16 May 2017 17:05:32 +0200
> Andrey Konovalov <andreyknvl@google.com> wrote:
>
>> Hi,
>>
>> I've got the following error report while fuzzing the kernel with syzkaller.
>>
>> On commit 2ea659a9ef488125eb46da6eb571de5eae5c43f6 (4.12-rc1).
>>
>> A reproducer and .config are attached.
>
> This should fix it.

Hi Alan,

Someone else has already sent a couple of versions of a similar fix.

https://patchwork.ozlabs.org/patch/763832/

Thanks!

>
> commit 37b3fa4b617681f00cfa1f76d6d7716cc6d9f79a
> Author: Alan Cox <alan@llwyncelyn.cymru>
> Date:   Wed May 17 21:04:27 2017 +0100
>
>     hdlcdrv: Fix division by zero when bitrate is unset
>
>     The code attempts to check for out of range calibration. What it forgets to do
>     is check for the 0 bitrate case. As a result the range check itself oopses the
>     kernel.
>
>     Found by Andrey Konovalov using Syzkaller.
>
>     Signed-off-by: Alan Cox <alan@linux.intel.com>
>
> diff --git a/drivers/net/hamradio/hdlcdrv.c b/drivers/net/hamradio/hdlcdrv.c
> index 8c3633c..9f34a48 100644
> --- a/drivers/net/hamradio/hdlcdrv.c
> +++ b/drivers/net/hamradio/hdlcdrv.c
> @@ -576,7 +576,7 @@ static int hdlcdrv_ioctl(struct net_device *dev, struct ifreq *ifr, int cmd)
>         case HDLCDRVCTL_CALIBRATE:
>                 if(!capable(CAP_SYS_RAWIO))
>                         return -EPERM;
> -               if (bi.data.calibrate > INT_MAX / s->par.bitrate)
> +               if (!s->par.bitrate || bi.data.calibrate > INT_MAX / s->par.bitrate)
>                         return -EINVAL;
>                 s->hdlctx.calibrate = bi.data.calibrate * s->par.bitrate / 16;
>                 return 0;

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Re: drivers/net/hamradio: divide error in hdlcdrv_ioctl Alan Cox <gnomes@lxorguk.ukuu.org.uk> - 2017-05-17 22:10 +0200
  Re: drivers/net/hamradio: divide error in hdlcdrv_ioctl Andrey Konovalov <andreyknvl@google.com> - 2017-05-19 02:30 +0200

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