netdev - Re: [PATCH net-next 3/6] rtnetlink: switch rtnl_link_get_slave_info_data

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Message-ID: <66b0f2eb-1b32-f7f5-046d-93c4febd1a41@gmail.com>
Date:   Thu, 10 Aug 2017 10:17:07 -0600
From:   David Ahern <dsahern@...il.com>
To:     Florian Westphal <fw@...len.de>, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 3/6] rtnetlink: switch
 rtnl_link_get_slave_info_data_size to rcu

On 8/10/17 8:52 AM, Florian Westphal wrote:
> David Ahern reports following splat:
>  RTNL: assertion failed at net/core/dev.c (5717)
>  netdev_master_upper_dev_get+0x5f/0x70
>  if_nlmsg_size+0x158/0x240
>  rtnl_calcit.isra.26+0xa3/0xf0
> 
> rtnl_link_get_slave_info_data_size currently assumes RTNL protection, but
> there appears to be no hard requirement for this, so use rcu instead.
> 
> At the time of this writing, there are three 'get_slave_size' callbacks
> (now invoked under rcu): bond_get_slave_size, vrf_get_slave_size and
> br_port_get_slave_size, all return constant only (i.e. they don't sleep).
> 
> Fixes: 6853dd488119 ("rtnetlink: protect handler table with rcu")
> Reported-by: David Ahern <dsahern@...il.com>
> Signed-off-by: Florian Westphal <fw@...len.de>
> ---
>  net/core/rtnetlink.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)

Acked-by: David Ahern <dsahern@...il.com>