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

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Message-ID: <20191025154903.GH31224@sasha-vm>
Date:   Fri, 25 Oct 2019 11:49:03 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Mahesh Bandewar <maheshb@...gle.com>,
        "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 5.3 12/33] blackhole_netdev: fix syzkaller
 reported issue

On Fri, Oct 25, 2019 at 09:54:44AM -0400, Sasha Levin wrote:
>From: Mahesh Bandewar <maheshb@...gle.com>
>
>[ 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@...emloft.net>
>Signed-off-by: Sasha Levin <sashal@...nel.org>

I've dropped this patch.

-- 
Thanks,
Sasha