netdev - Re: [PATCH net] ipv6/ndisc: Preserve IPv6 control buffer if protocol error handlers are called

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Message-Id: <20181026.155821.1494940486796676776.davem@davemloft.net>
Date:   Fri, 26 Oct 2018 15:58:21 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     sbrivio@...hat.com
Cc:     yoshfuji@...ux-ipv6.org, netdev@...r.kernel.org
Subject: Re: [PATCH net] ipv6/ndisc: Preserve IPv6 control buffer if
 protocol error handlers are called

From: Stefano Brivio <sbrivio@...hat.com>
Date: Wed, 24 Oct 2018 14:37:21 +0200

> Commit a61bbcf28a8c ("[NET]: Store skb->timestamp as offset to a base
> timestamp") introduces a neighbour control buffer and zeroes it out in
> ndisc_rcv(), as ndisc_recv_ns() uses it.
> 
> Commit f2776ff04722 ("[IPV6]: Fix address/interface handling in UDP and
> DCCP, according to the scoping architecture.") introduces the usage of the
> IPv6 control buffer in protocol error handlers (e.g. inet6_iif() in
> present-day __udp6_lib_err()).
> 
> Now, with commit b94f1c0904da ("ipv6: Use icmpv6_notify() to propagate
> redirect, instead of rt6_redirect()."), we call protocol error handlers
> from ndisc_redirect_rcv(), after the control buffer is already stolen and
> some parts are already zeroed out. This implies that inet6_iif() on this
> path will always return zero.
> 
> This gives unexpected results on UDP socket lookup in __udp6_lib_err(), as
> we might actually need to match sockets for a given interface.
> 
> Instead of always claiming the control buffer in ndisc_rcv(), do that only
> when needed.
> 
> Fixes: b94f1c0904da ("ipv6: Use icmpv6_notify() to propagate redirect, instead of rt6_redirect().")
> Signed-off-by: Stefano Brivio <sbrivio@...hat.com>

Applied and queued up for -stable, thank you.