From: Roman Gushchin Subject: Re: [PATCH] net: check net.core.somaxconn sysctl values Date: Wed, 31 Jul 2013 19:03:23 +0400 Message-ID: <51F9273B.2020408@yandex-team.ru> References: <51F917CF.7010905@yandex-team.ru> <1375281457.10515.98.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: "David S. Miller" , raise.sail@gmail.com, ebiederm@xmission.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Eric Dumazet Return-path: In-Reply-To: <1375281457.10515.98.camel@edumazet-glaptop> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 31.07.2013 18:37, Eric Dumazet wrote: > 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 >> --- >> 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 ;) Ok :) > Based on a prior patch from Changli Gao > > Reported-by: Changli Gao > Suggested-by: Eric Dumazet > > Acked-by: Eric Dumazet > Thanks! PS I've forwarded your letter back to the lkml by mistake. Sorry) Regards, Roman