Re: [PATCH AUTOSEL 5.3 12/33] blackhole_netdev: fix syzkaller reported issue

[Sasha Levin]

On Fri, Oct 25, 2019 at 09:54:44AM -0400, Sasha Levin wrote:
> From: Mahesh Bandewar <maheshb@xxxxxxxxxx>
>
> [ Upstream commit b0818f80c8c1bc215bba276bd61c216014fab23b ]
>
> While invalidating the dst, we assign backhole_netdev instead of
> loopback device. However, this device does not have idev pointer
> and hence no ip6_ptr even if IPv6 is enabled. Possibly this has
> triggered the syzbot reported crash.
>
> The syzbot report does not have reproducer, however, this is the
> only device that doesn't have matching idev created.
>
> Crash instruction is :
>
> static inline bool ip6_ignore_linkdown(const struct net_device *dev)
> {
>        const struct inet6_dev *idev = __in6_dev_get(dev);
>
>        return !!idev->cnf.ignore_routes_with_linkdown; <= crash
> }
>
> Also ipv6 always assumes presence of idev and never checks for it
> being NULL (as does the above referenced code). So adding a idev
> for the blackhole_netdev to avoid this class of crashes in the future.
>
> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

I've dropped this patch.

--
Thanks,
Sasha