Commit 5f671d6b authored by Roman Gushchin's avatar Roman Gushchin Committed by David S. Miller

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.

$ 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

$ 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: default avatarRoman Gushchin <>
Reported-by: default avatarChangli Gao <>
Suggested-by: default avatarEric Dumazet <>
Acked-by: default avatarEric Dumazet <>
Signed-off-by: default avatarDavid S. Miller <>
parent 3508ea33
......@@ -21,7 +21,9 @@
#include <net/net_ratelimit.h>
#include <net/busy_poll.h>
static int zero = 0;
static int one = 1;
static int ushort_max = USHRT_MAX;
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,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec
.extra1 = &zero,
.extra2 = &ushort_max,
.proc_handler = proc_dointvec_minmax
{ }
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