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

[Sabrina Dubroca <sd@queasysnail.net>]

2018-10-24, 14:37:21 +0200, Stefano Brivio wrote:
> 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@redhat.com>

Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>

-- 
Sabrina