Re: [PATCH net v2] ipv6: fix access to non-linear packet in ndisc_fill_redirect_hdr_option()

From: Lorenzo Bianconi <redacted>
Date: Thu,  8 Mar 2018 17:00:02 +0100

Fix the following slab-out-of-bounds kasan report in
ndisc_fill_redirect_hdr_option when the incoming ipv6 packet is not
linear and the accessed data are not in the linear data region of orig_skb.

 ...

The test scenario to trigger the issue consists of 4 devices:
- H0: data sender, connected to LAN0
- H1: data receiver, connected to LAN1
- GW0 and GW1: routers between LAN0 and LAN1. Both of them have an
  ethernet connection on LAN0 and LAN1
On H{0,1} set GW0 as default gateway while on GW0 set GW1 as next hop for
data from LAN0 to LAN1.
Moreover create an ip6ip6 tunnel between H0 and H1 and send 3 concurrent
data streams (TCP/UDP/SCTP) from H0 to H1 through ip6ip6 tunnel (send
buffer size is set to 16K). While data streams are active flush the route
cache on HA multiple times.
I have not been able to identify a given commit that introduced the issue
since, using the reproducer described above, the kasan report has been
triggered from 4.14 and I have not gone back further.

Reported-by: Jianlin Shi <redacted>
Reviewed-by: Stefano Brivio <redacted>
Reviewed-by: Eric Dumazet <redacted>
Signed-off-by: Lorenzo Bianconi <redacted>

Applied and queued up for -stable, thanks!