netdev - Re: [PATCH net-next 1/2] net: neighbour: prohibit negative value for unres_qlen

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Date:	Wed, 05 Dec 2012 16:26:05 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	shanwei88@...il.com
Cc:	eric.dumazet@...il.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next 1/2] net: neighbour: prohibit negative value
 for unres_qlen_bytes parameter

From: Shan Wei <shanwei88@...il.com>
Date: Wed, 05 Dec 2012 12:49:15 +0800

> From: Shan Wei <davidshan@...cent.com>
> 
> unres_qlen_bytes and unres_qlen are int type.
> But multiple relation(unres_qlen_bytes = unres_qlen * SKB_TRUESIZE(ETH_FRAME_LEN))
> will cause type overflow when seting unres_qlen. e.g.
> 
> $ echo 1027506 > /proc/sys/net/ipv4/neigh/eth1/unres_qlen
> $ cat /proc/sys/net/ipv4/neigh/eth1/unres_qlen
> 1182657265
> $ cat /proc/sys/net/ipv4/neigh/eth1/unres_qlen_bytes 
> -2147479756
> 
> The gutted value is not that we setting。
> But user/administrator don't know this is caused by int type overflow.
> 
> what's more, it is meaningless and even dangerous that unres_qlen_bytes is set
> with negative number. Because, for unresolved neighbour address, kernel will cache packets
> without limit in __neigh_event_send()(e.g. (u32)-1 = 2GB).
> 
> 
> Signed-off-by: Shan Wei <davidshan@...cent.com>

Applied.
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