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Date:   Tue, 6 Apr 2021 11:18:55 +0100
From:   Phillip Potter <phil@philpotter.co.uk>
To:     David Miller <davem@davemloft.net>
Cc:     kuba@kernel.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] net: tun: set tun->dev->addr_len during TUNSETLINK
 processing
Message-ID: <YGw1jx5zO4+Wz5Md@equinox>
References: <20210405113555.9419-1-phil@philpotter.co.uk>
 <20210405.145921.1248097047641627556.davem@davemloft.net>
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On Mon, Apr 05, 2021 at 02:59:21PM -0700, David Miller wrote:
> From: Phillip Potter <phil@philpotter.co.uk>
> Date: Mon,  5 Apr 2021 12:35:55 +0100
> 
> > When changing type with TUNSETLINK ioctl command, set tun->dev->addr_len
> > to match the appropriate type, using new tun_get_addr_len utility function
> > which returns appropriate address length for given type. Fixes a
> > KMSAN-found uninit-value bug reported by syzbot at:
> > https://syzkaller.appspot.com/bug?id=0766d38c656abeace60621896d705743aeefed51
> > 
> > Reported-by: syzbot+001516d86dbe88862cec@syzkaller.appspotmail.com
> > Signed-off-by: Phillip Potter <phil@philpotter.co.uk>
> > ---
> >  drivers/net/tun.c | 48 +++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 48 insertions(+)
> > 
> > diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> > index 978ac0981d16..56c26339ee3b 100644
> > --- a/drivers/net/tun.c
> > +++ b/drivers/net/tun.c
> > @@ -69,6 +69,14 @@
> >  #include <linux/bpf.h>
> >  #include <linux/bpf_trace.h>
> >  #include <linux/mutex.h>
> > +#include <linux/ieee802154.h>
> > +#include <linux/if_ltalk.h>
> > +#include <uapi/linux/if_fddi.h>
> > +#include <uapi/linux/if_hippi.h>
> > +#include <uapi/linux/if_fc.h>
> > +#include <net/ax25.h>
> > +#include <net/rose.h>
> > +#include <net/6lowpan.h>
> >  
> >  #include <linux/uaccess.h>
> >  #include <linux/proc_fs.h>
> > @@ -2925,6 +2933,45 @@ static int tun_set_ebpf(struct tun_struct *tun, struct tun_prog __rcu **prog_p,
> >  	return __tun_set_ebpf(tun, prog_p, prog);
> >  }
> >  
> > +/* Return correct value for tun->dev->addr_len based on tun->dev->type. */
> > +static inline unsigned char tun_get_addr_len(unsigned short type)
> > +{
> 
> Please do not use inline in foo.c files, let the compiler decide.
> 
> Thanks.

Dear David,

Thank you for the feedback, I will resend.

Regards,
Phil