netdev - Re: [PATCH net] ipv6: addrconf: break critical section in addrconf_verify

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Message-ID: <20180127085250.GA24639@splinter>
Date:   Sat, 27 Jan 2018 10:52:50 +0200
From:   Ido Schimmel <idosch@...sch.org>
To:     Eric Dumazet <eric.dumazet@...il.com>
Cc:     Heiner Kallweit <hkallweit1@...il.com>,
        David Miller <davem@...emloft.net>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net] ipv6: addrconf: break critical section in
 addrconf_verify_rtnl()

On Fri, Jan 26, 2018 at 04:10:43PM -0800, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> Heiner reported a lockdep splat [1]
> 
> This is caused by attempting GFP_KERNEL allocation while RCU lock is
> held and BH blocked.
> 
> We believe that addrconf_verify_rtnl() could run for a long period,
> so instead of using GFP_ATOMIC here as Ido suggested, we should break
> the critical section and restart it after the allocation.

[...]

> Fixes: f3d9832e56c4 ("ipv6: addrconf: cleanup locking in ipv6_add_addr")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Heiner Kallweit <hkallweit1@...il.com>

Reviewed-by: Ido Schimmel <idosch@...lanox.com>

Thanks!