netdev - Re: [PATCH net-next] hv_netvsc: fix a race between netvsc_send() and netvsc_init

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Message-Id: <20161021.112801.585243295635293094.davem@davemloft.net>
Date:   Fri, 21 Oct 2016 11:28:01 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     vkuznets@...hat.com
Cc:     netdev@...r.kernel.org, sthemmin@...rosoft.com,
        devel@...uxdriverproject.org, linux-kernel@...r.kernel.org,
        kys@...rosoft.com, haiyangz@...rosoft.com
Subject: Re: [PATCH net-next] hv_netvsc: fix a race between netvsc_send()
 and netvsc_init_buf()

From: Vitaly Kuznetsov <vkuznets@...hat.com>
Date: Wed, 19 Oct 2016 15:53:01 +0200

> Fix in commit 880988348270 ("hv_netvsc: set nvdev link after populating
> chn_table") turns out to be incomplete. A crash in
> netvsc_get_next_send_section() is observed on mtu change when the device
> is under load. The race I identified is: if we get to netvsc_send() after
> we set net_device_ctx->nvdev link in netvsc_device_add() but before we
> finish netvsc_connect_vsp()->netvsc_init_buf() send_section_map is not
> allocated and we crash. Unfortunately we can't set net_device_ctx->nvdev
> link after the netvsc_init_buf() call as during the negotiation we need
> to receive packets and on the receive path we check for it. It would
> probably be possible to split nvdev into a pair of nvdev_in and nvdev_out
> links and check them accordingly in get_outbound_net_device()/
> get_inbound_net_device() but this looks like an overkill.
> 
> Check that send_section_map is allocated in netvsc_send().
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>

Applied, thanks.