linux-kernel - Re: [PATCH] staging: wlan-ng/p80211 : check userspacebuf size for sanity

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Message-ID: <YDO0vtJyyGSSi44n@karthik-strix-linux.karthek.com>
Date:   Mon, 22 Feb 2021 19:12:22 +0530
From:   karthek <mail@...thek.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: wlan-ng/p80211 : check userspacebuf size for
 sanity

On Mon, Feb 22, 2021 at 04:21:33PM +0300, Dan Carpenter wrote:
> On Mon, Feb 22, 2021 at 06:16:24PM +0530, karthek wrote:
> > currently p80211knetdev_do_ioctl() is testing user passed
> > struct ifreq for sanity by checking for presence of a magic number,
> > in addition to that also check size field, preventing buffer overflow
> > before passing data to p80211req_dorequest() which casts it
> > to *struct p80211msg
> > 
> > Signed-off-by: karthek <mail@...thek.com>
> > ---
> > is this correct?
> > is it necessary to check for size in addition to magicnum?
> > did i even understand the problem correctly?
> > 
> >  drivers/staging/wlan-ng/p80211netdev.c | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/staging/wlan-ng/p80211netdev.c b/drivers/staging/wlan-ng/p80211netdev.c
> > index 70570e8a5..c7b78d870 100644
> > --- a/drivers/staging/wlan-ng/p80211netdev.c
> > +++ b/drivers/staging/wlan-ng/p80211netdev.c
> > @@ -568,7 +568,10 @@ static int p80211knetdev_do_ioctl(struct net_device *dev,
> >  		result = -EINVAL;
> >  		goto bail;
> >  	}
> > -
> > +	if (req->len < sizeof(struct p80211msg)) {
> > +		result = -EINVAL;
> > +		goto bail;
> > +	}
> 
> Please don't send private emails.  Always CC the list.
sorry
> 
> That's only a partial solution.  You need to check in p80211req_handlemsg()
> as well and probably other places.
currently p80211req_handlemsg() is only referenced in p80211req_dorequest()
can we check that there instead?
> 
> regards,
> dan carpenter
>