linux-kernel - Re: [PATCH] net: check net.core.somaxconn sysctl values

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Date:	Fri, 02 Aug 2013 15:19:15 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	klamm@...dex-team.ru
Cc:	eric.dumazet@...il.com, raise.sail@...il.com,
	ebiederm@...ssion.com, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] net: check net.core.somaxconn sysctl values

From: Roman Gushchin <klamm@...dex-team.ru>
Date: Fri,  2 Aug 2013 18:36:40 +0400

> It's possible to assign an invalid value to the net.core.somaxconn
> sysctl variable, because there is no checks at all.
> 
> The sk_max_ack_backlog field of the sock structure is defined as
> unsigned short. Therefore, the backlog argument in inet_listen()
> shouldn't exceed USHRT_MAX. The backlog argument in the listen() syscall
> is truncated to the somaxconn value. So, the somaxconn value shouldn't
> exceed 65535 (USHRT_MAX).
> Also, negative values of somaxconn are meaningless.
> 
> before:
> $ sysctl -w net.core.somaxconn=256
> net.core.somaxconn = 256
> $ sysctl -w net.core.somaxconn=65536
> net.core.somaxconn = 65536
> $ sysctl -w net.core.somaxconn=-100
> net.core.somaxconn = -100
> 
> after:
> $ sysctl -w net.core.somaxconn=256
> net.core.somaxconn = 256
> $ sysctl -w net.core.somaxconn=65536
> error: "Invalid argument" setting key "net.core.somaxconn"
> $ sysctl -w net.core.somaxconn=-100
> error: "Invalid argument" setting key "net.core.somaxconn"
> 
> Based on a prior patch from Changli Gao.
> 
> Signed-off-by: Roman Gushchin <klamm@...dex-team.ru>
> Reported-by: Changli Gao <xiaosuo@...il.com>
> Suggested-by: Eric Dumazet <edumazet@...gle.com>
> Acked-by: Eric Dumazet <edumazet@...gle.com>

Applied, thanks.
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