linux-kernel - Re: [PATCH 5.10 09/43] netrom: fix copying in user data in nr

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Date:   Mon, 10 Jan 2022 13:14:40 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Pavel Machek <pavel@...x.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Christoph Hellwig <hch@....de>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 5.10 09/43] netrom: fix copying in user data in
 nr_setsockopt

On Mon, Jan 10, 2022 at 11:07:08AM +0100, Pavel Machek wrote:
> Hi!
> 
> > From: Christoph Hellwig <hch@....de>
> > 
> > commit 3087a6f36ee028ec095c04a8531d7d33899b7fed upstream.
> > 
> > This code used to copy in an unsigned long worth of data before
> > the sockptr_t conversion, so restore that.
> 
> Maybe, but then	the size checks	need to	be updated, too.
> 
> > Reported-by: Dan Carpenter <dan.carpenter@...cle.com>
> > Signed-off-by: Christoph Hellwig <hch@....de>
> > Signed-off-by: David S. Miller <davem@...emloft.net>
> > Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> > ---
> >  net/netrom/af_netrom.c |    2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > --- a/net/netrom/af_netrom.c
> > +++ b/net/netrom/af_netrom.c
> > @@ -306,7 +306,7 @@ static int nr_setsockopt(struct socket *
> >  	if (optlen < sizeof(unsigned int))
> 
> This should   be   < sizeof(unsigned long)) ... AFAICT.
> 
> >  		return -EINVAL;

Yeah.  This patch isn't right.  I sent a follow on that changes
everything to unsigned int.  Originally it was:

	if (get_user(opt, (unsigned int __user *)optval))

Which copies an unsigned int from the user into an unsigned long opt
variable.

My fix is required to fix an uninitialized data bug in a7b75c5a8c41
("net: pass a sockptr_t into ->setsockopt").  It would be sligthly more
complicated to just backport my fix without first backporting this one
and it would look sort of weird.  So I think it's better to backport
this and then mine.

regards,
dan carpenter