Date:   Wed, 8 Dec 2021 11:34:14 -0500
From:   Stephen Suryaputra <ssuryaextr@gmail.com>
To:     David Ahern <dsahern@gmail.com>
Cc:     Florian Westphal <fw@strlen.de>,
        Andrea Mayer <andrea.mayer@uniroma2.it>,
        Andrea Righi <andrea.righi@canonical.com>,
        "David S. Miller" <davem@davemloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        David Ahern <dsahern@kernel.org>,
        Jakub Kicinski <kuba@kernel.org>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        Ahmed Abdelsalam <ahabdels@gmail.com>,
        Paolo Lungaroni <paolo.lungaroni@uniroma2.it>,
        Stefano Salsano <stefano.salsano@uniroma2.it>
Subject: Re: [PATCH] ipv6: fix NULL pointer dereference in ip6_output()
Message-ID: <20211208163414.GA747@ICIPI.localdomain>
References: <20211206163447.991402-1-andrea.righi@canonical.com>
 <cfedb3e3-746a-d052-b3f1-09e4b20ad061@gmail.com>
 <20211208012102.844ec898c10339e99a69db5f@uniroma2.it>
 <a20d6c2f-f64f-b432-f214-c1f2b64fdf81@gmail.com>
 <20211208105113.GE30918@breakpoint.cc>
 <d6cacd7d-732c-4fad-576d-a7e9d9ca9537@gmail.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <d6cacd7d-732c-4fad-576d-a7e9d9ca9537@gmail.com>
Precedence: bulk

On Wed, Dec 08, 2021 at 08:46:37AM -0700, David Ahern wrote:
> On 12/8/21 3:51 AM, Florian Westphal wrote:
> > David Ahern <dsahern@gmail.com> wrote:
> >> On 12/7/21 5:21 PM, Andrea Mayer wrote:
> >>> +        IP6CB(skb)->iif = skb->skb_iif;
> >>>          [...]
> >>>
> >>> What do you think?
> >>>
> >>
> >> I like that approach over the need for a fall back in core ipv6 code.
> > 
> > What if the device is removed after ->iif assignment and before dev lookup?
> > 
> 
> good point. SR6 should make sure the iif is not cleared, and the
> fallback to the skb->dev is still needed in case of delete.

Thanks for the explanation. I was thinking that ->iif can safely be
assumed to be valid. Florian's point that device can be removed is a
good one. My bad for not putting the check and thanks for fixing.