netdev - Re: [PATCH] ieee802154: mcr20a: read out of bounds in mcr20a_set

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Message-ID: <20180830075421.czsb5pa5b2vygp2m@mwanda>
Date:   Thu, 30 Aug 2018 10:54:21 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Xue Liu <liuxuenetmail@...il.com>
Cc:     "alex. aring" <alex.aring@...il.com>,
        Stefan Schmidt <stefan@...enfreihafen.org>,
        "David S. Miller" <davem@...emloft.net>,
        linux-wpan - ML <linux-wpan@...r.kernel.org>,
        netdev@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] ieee802154: mcr20a: read out of bounds in
 mcr20a_set_channel()

On Wed, Aug 29, 2018 at 07:50:51PM +0200, Xue Liu wrote:
> Hello Dan,
> 
> 
> On Wed, 29 Aug 2018 at 16:49, Dan Carpenter <dan.carpenter@...cle.com>
> wrote:
> 
> > The "channel" variable can be any u8 value.  We need to make sure we
> > don't read outside of the PLL_INT[] or PLL_FRAC[] arrays.
> >
> I think the “channel” variable can not be any u8 value. This values is
> already checked before set_channel function is called.
> https://github.com/torvalds/linux/blob/master/net/ieee802154/nl802154.c#L978

Oh...  Hm...  I should have reviewed more carefully.  This patch isn't
correct.  But there may still be a bug.  What Smatch is worried about is
the other call tree:

ieee802154_start_req() calls (struct ieee802154_mlme_ops)->start_req
  -> mac802154_mlme_start_req()
     -> mac802154_dev_set_page_channel()
        -> drv_set_channel() calls local->ops->set_channel(&local->hw, page, channel);
           -> mcr20a_set_channel()

So maybe we could move the check from nl802154_set_channel() to
drv_set_channel() so channel is checked on both call trees.

regards,
dan carpenter