netdev - Re: [PATCH net-next] net/sched: act_ct: fix lockdep splat in tcf_ct_flow_table

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Date:   Sun, 08 Mar 2020 21:48:37 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     edumazet@...gle.com
Cc:     netdev@...r.kernel.org, eric.dumazet@...il.com, paulb@...lanox.com,
        jiri@...lanox.com, syzkaller@...glegroups.com
Subject: Re: [PATCH net-next] net/sched: act_ct: fix lockdep splat in
 tcf_ct_flow_table_get

From: Eric Dumazet <edumazet@...gle.com>
Date: Sun,  8 Mar 2020 14:27:48 -0700

> Convert zones_lock spinlock to zones_mutex mutex,
> and struct (tcf_ct_flow_table)->ref to a refcount,
> so that control path can use regular GFP_KERNEL allocations
> from standard process context. This is more robust
> in case of memory pressure.
> 
> The refcount is needed because tcf_ct_flow_table_put() can
> be called from RCU callback, thus in BH context.
> 
> The issue was spotted by syzbot, as rhashtable_init()
> was called with a spinlock held, which is bad since GFP_KERNEL
> allocations can sleep.
> 
> Note to developers : Please make sure your patches are tested
> with CONFIG_DEBUG_ATOMIC_SLEEP=y
 ...
> Fixes: c34b961a2492 ("net/sched: act_ct: Create nf flow table per zone")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Cc: Paul Blakey <paulb@...lanox.com>
> Cc: Jiri Pirko <jiri@...lanox.com>
> Reported-by: syzbot <syzkaller@...glegroups.com>

Applied, thanks.