net: check net.core.somaxconn sysctl values
authorRoman Gushchin <klamm@yandex-team.ru>
Fri, 2 Aug 2013 14:36:40 +0000 (18:36 +0400)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Sat, 14 Sep 2013 13:54:54 +0000 (06:54 -0700)
commit4691236cedfb12e2644f4c84b4b14a6882e1fd7b
treecfb7091aad2e26a5dced9bcf44d378691e3ff707
parentb4f55925ace5646d72df5af6fdab74fdbb288229
net: check net.core.somaxconn sysctl values

[ Upstream commit 5f671d6b4ec3e6d66c2a868738af2cdea09e7509 ]

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@yandex-team.ru>
Reported-by: Changli Gao <xiaosuo@gmail.com>
Suggested-by: Eric Dumazet <edumazet@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
net/core/sysctl_net_core.c