[INET]: local port range robustness
Expansion of original idea from Denis V. Lunev <den@openvz.org>
Add robustness and locking to the local_port_range sysctl.
1. Enforce that low < high when setting.
2. Use seqlock to ensure atomic update.
The locking might seem like overkill, but there are
cases where sysadmin might want to change value in the
middle of a DoS attack.
Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index fb66262..fac6398 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -279,19 +279,18 @@
int ret;
if (!snum) {
- int low = sysctl_local_port_range[0];
- int high = sysctl_local_port_range[1];
- int range = high - low;
- int i;
- int port;
+ int i, remaining, low, high, port;
static u32 hint;
u32 offset = hint + inet_sk_port_offset(sk);
struct hlist_node *node;
struct inet_timewait_sock *tw = NULL;
+ inet_get_local_port_range(&low, &high);
+ remaining = high - low;
+
local_bh_disable();
- for (i = 1; i <= range; i++) {
- port = low + (i + offset) % range;
+ for (i = 1; i <= remaining; i++) {
+ port = low + (i + offset) % remaining;
head = &hinfo->bhash[inet_bhashfn(port, hinfo->bhash_size)];
spin_lock(&head->lock);
