FYI: Re: [PATCH] net: check net.core.somaxconn sysctl values

[Roman Gushchin <klamm@yandex-team.ru>]

-------- Original Message --------
Subject: Re: [PATCH] net: check net.core.somaxconn sysctl values
Date: Wed, 31 Jul 2013 07:37:37 -0700
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Roman Gushchin <klamm@yandex-team.ru>
CC: David S. Miller <davem@davemloft.net>, raise.sail@gmail.com,  ebiederm@xmission.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org

On Wed, 2013-07-31 at 17:57 +0400, Roman Gushchin wrote:
> 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"
>
> Signed-off-by: Roman Gushchin <klamm@yandex-team.ru>
> ---
>   net/core/sysctl_net_core.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)


We had a discussion about this one month ago, as Changli Gao posted a
patch. http://patchwork.ozlabs.org/patch/255460/

So proper credits would be nice ;)

Based on a prior patch from Changli Gao

Reported-by: Changli Gao <xiaosuo@gmail.com>
Suggested-by: Eric Dumazet <edumazet@google.com>

Acked-by: Eric Dumazet <edumazet@google.com>