Commit 5f671d6b authored Aug 02, 2013 by Roman Gushchin Committed by David S. Miller Aug 02, 2013

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>

parent 3508ea33

net/core/sysctl_net_core.c

+5 −1

Original line number	Original line	Diff line number	Diff line
	@@ -21,7 +21,9 @@
	#include <net/net_ratelimit.h>		#include <net/net_ratelimit.h>
	#include <net/busy_poll.h>		#include <net/busy_poll.h>

			static int zero = 0;
	static int one = 1;		static int one = 1;
			static int ushort_max = USHRT_MAX;

	#ifdef CONFIG_RPS		#ifdef CONFIG_RPS
	static int rps_sock_flow_sysctl(struct ctl_table *table, int write,		static int rps_sock_flow_sysctl(struct ctl_table *table, int write,
	@@ -339,7 +341,9 @@ static struct ctl_table netns_core_table[] = {
	.data = &init_net.core.sysctl_somaxconn,		.data = &init_net.core.sysctl_somaxconn,
	.maxlen = sizeof(int),		.maxlen = sizeof(int),
	.mode = 0644,		.mode = 0644,
	.proc_handler = proc_dointvec		.extra1 = &zero,
			.extra2 = &ushort_max,
			.proc_handler = proc_dointvec_minmax
	},		},
	{ }		{ }
	};		};