net: check net.core.somaxconn sysctl values
authorRoman Gushchin <klamm@yandex-team.ru>
Fri, 2 Aug 2013 14:36:40 +0000 (18:36 +0400)
committerDavid S. Miller <davem@davemloft.net>
Fri, 2 Aug 2013 22:18:53 +0000 (15:18 -0700)
commit5f671d6b4ec3e6d66c2a868738af2cdea09e7509
treeb117717db9f3b70118095c0e12a0acb1daad5591
parent3508ea333ed5414561af4c818b3b80c0acca1845
net: check net.core.somaxconn sysctl values

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>
net/core/sysctl_net_core.c