netdev - Re: [PATCH net-next] tcp: fix a potential deadlock in tcp_get

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Date:	Fri, 22 May 2015 13:50:42 -0400 (EDT)
From:	David Miller <davem@...hat.com>
To:	eric.dumazet@...il.com
Cc:	mleitner@...hat.com, edumazet@...gle.com, netdev@...r.kernel.org,
	ycheng@...gle.com, mattmathis@...gle.com, cgallek@...gle.com,
	kafai@...com
Subject: Re: [PATCH net-next] tcp: fix a potential deadlock in
 tcp_get_info()

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Thu, 21 May 2015 21:51:19 -0700

> From: Eric Dumazet <edumazet@...gle.com>
> 
> Taking socket spinlock in tcp_get_info() can deadlock, as
> inet_diag_dump_icsk() holds the &hashinfo->ehash_locks[i],
> while packet processing can use the reverse locking order.
> 
> We could avoid this locking for TCP_LISTEN states, but lockdep would
> certainly get confused as all TCP sockets share same lockdep classes.
 ...
> Lets use u64_sync infrastructure instead. As a bonus, 64bit
> arches get optimized, as these are nop for them.
> 
> Fixes: 0df48c26d841 ("tcp: add tcpi_bytes_acked to tcp_info")
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>

This bug exists in 'net' so I've applied it there.

Thanks Eric.
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