ICMP messages are ratelimited :
After the blamed commits, the two rate limiters are applied in this order:
1) host wide ratelimit (icmp_global_allow())
2) Per destination ratelimit (inetpeer based)
In order to avoid side-channels attacks, we need to apply
the per destination check first.
This patch makes the following change :
1) icmp_global_allow() checks if the host wide limit is reached.
But credits are not yet consumed. This is deferred to 3)
2) The per destination limit is checked/updated.
This might add a new node in inetpeer tree.
3) icmp_global_consume() consumes tokens if prior operations succeeded.
This means that host wide ratelimit is still effective
in keeping inetpeer tree small even under DDOS.
As a bonus, I removed icmp_global.lock as the fast path
can use a lock-free operation.
Fixes: c0303efeab73 ("net: reduce cycles spend on ICMP replies that gets rate limited")
Fixes: 4cdf507d5452 ("icmp: add a global rate limitation")
Reported-by: Keyu Man <keyu.man@xxxxxxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Jesper Dangaard Brouer <hawk@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
include/net/ip.h | 2 +
net/ipv4/icmp.c | 103 ++++++++++++++++++++++++++---------------------
net/ipv6/icmp.c | 28 ++++++++-----
3 files changed, 76 insertions(+), 57 deletions(-)
diff --git a/include/net/ip.h b/include/net/ip.h
index c5606cadb1a552f3e282a5e1e721fd47b07432b2..82248813619e3f21e09d52976accbdc76c7668c2 100644
--- a/include/net/ip.h
+++ b/include/net/ip.h
@@ -795,6 +795,8 @@ static inline void ip_cmsg_recv(struct msghdr *msg, struct sk_buff *skb)
}
bool icmp_global_allow(void);
+void icmp_global_consume(void);
+
extern int sysctl_icmp_msgs_per_sec;
extern int sysctl_icmp_msgs_burst;
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index b8f56d03fcbb62970a828e20dd9f05fcede2d552..0078e8fb2e86d0552ef85eb5bf5bef947b0f1c3d 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -224,57 +224,59 @@ int sysctl_icmp_msgs_per_sec __read_mostly = 1000;
int sysctl_icmp_msgs_burst __read_mostly = 50;
static struct {
- spinlock_t lock;
- u32 credit;
+ atomic_t credit;
u32 stamp;
-} icmp_global = {
- .lock = __SPIN_LOCK_UNLOCKED(icmp_global.lock),
-};
+} icmp_global;
/**
* icmp_global_allow - Are we allowed to send one more ICMP message ?
*
* Uses a token bucket to limit our ICMP messages to ~sysctl_icmp_msgs_per_sec.
* Returns false if we reached the limit and can not send another packet.
- * Note: called with BH disabled
+ * Works in tandem with icmp_global_consume().
*/
bool icmp_global_allow(void)
{
- u32 credit, delta, incr = 0, now = (u32)jiffies;
- bool rc = false;
+ u32 delta, now, oldstamp;
+ int incr, new, old;
- /* Check if token bucket is empty and cannot be refilled
- * without taking the spinlock. The READ_ONCE() are paired
- * with the following WRITE_ONCE() in this same function.
+ /* Note: many cpus could find this condition true.
+ * Then later icmp_global_consume() could consume more credits,
+ * this is an acceptable race.
*/
- if (!READ_ONCE(icmp_global.credit)) {
- delta = min_t(u32, now - READ_ONCE(icmp_global.stamp), HZ);
- if (delta < HZ / 50)
- return false;
- }
+ if (atomic_read(&icmp_global.credit) > 0)
+ return true;
- spin_lock(&icmp_global.lock);
- delta = min_t(u32, now - icmp_global.stamp, HZ);
- if (delta >= HZ / 50) {
- incr = READ_ONCE(sysctl_icmp_msgs_per_sec) * delta / HZ;
- if (incr)
- WRITE_ONCE(icmp_global.stamp, now);
- }
- credit = min_t(u32, icmp_global.credit + incr,
- READ_ONCE(sysctl_icmp_msgs_burst));
- if (credit) {
- /* We want to use a credit of one in average, but need to randomize
- * it for security reasons.
- */
- credit = max_t(int, credit - get_random_u32_below(3), 0);
- rc = true;
+ now = jiffies;
+ oldstamp = READ_ONCE(icmp_global.stamp);
+ delta = min_t(u32, now - oldstamp, HZ);
+ if (delta < HZ / 50)
+ return false;
+
+ incr = READ_ONCE(sysctl_icmp_msgs_per_sec) * delta / HZ;
+ if (!incr)
+ return false;
+
+ if (cmpxchg(&icmp_global.stamp, oldstamp, now) == oldstamp) {
+ old = atomic_read(&icmp_global.credit);
+ do {
+ new = min(old + incr, READ_ONCE(sysctl_icmp_msgs_burst));
+ } while (!atomic_try_cmpxchg(&icmp_global.credit, &old, new));
}
- WRITE_ONCE(icmp_global.credit, credit);
- spin_unlock(&icmp_global.lock);
- return rc;
+ return true;
}
EXPORT_SYMBOL(icmp_global_allow);
+void icmp_global_consume(void)
+{
+ int credits = get_random_u32_below(3);
+
+ /* Note: this might make icmp_global.credit negative. */
+ if (credits)
+ atomic_sub(credits, &icmp_global.credit);
+}
+EXPORT_SYMBOL(icmp_global_consume);
+
static bool icmpv4_mask_allow(struct net *net, int type, int code)
{
if (type > NR_ICMP_TYPES)
@@ -291,14 +293,16 @@ static bool icmpv4_mask_allow(struct net *net, int type, int code)
return false;
}
-static bool icmpv4_global_allow(struct net *net, int type, int code)
+static bool icmpv4_global_allow(struct net *net, int type, int code,
+ bool *apply_ratelimit)
{
if (icmpv4_mask_allow(net, type, code))
return true;
- if (icmp_global_allow())
+ if (icmp_global_allow()) {
+ *apply_ratelimit = true;
return true;
-
+ }
__ICMP_INC_STATS(net, ICMP_MIB_RATELIMITGLOBAL);
return false;
}
@@ -308,15 +312,16 @@ static bool icmpv4_global_allow(struct net *net, int type, int code)
*/
static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
- struct flowi4 *fl4, int type, int code)
+ struct flowi4 *fl4, int type, int code,
+ bool apply_ratelimit)
{
struct dst_entry *dst = &rt->dst;
struct inet_peer *peer;
bool rc = true;
int vif;
- if (icmpv4_mask_allow(net, type, code))
- goto out;
+ if (!apply_ratelimit)
+ return true;
/* No rate limit on loopback */
if (dst->dev && (dst->dev->flags&IFF_LOOPBACK))
@@ -331,6 +336,8 @@ static bool icmpv4_xrlim_allow(struct net *net, struct rtable *rt,
out:
if (!rc)
__ICMP_INC_STATS(net, ICMP_MIB_RATELIMITHOST);
+ else
+ icmp_global_consume();
return rc;
}
@@ -402,6 +409,7 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
struct ipcm_cookie ipc;
struct rtable *rt = skb_rtable(skb);
struct net *net = dev_net(rt->dst.dev);
+ bool apply_ratelimit = false;
struct flowi4 fl4;
struct sock *sk;
struct inet_sock *inet;
@@ -413,11 +421,11 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
if (ip_options_echo(net, &icmp_param->replyopts.opt.opt, skb))
return;
- /* Needed by both icmp_global_allow and icmp_xmit_lock */
+ /* Needed by both icmpv4_global_allow and icmp_xmit_lock */
local_bh_disable();
- /* global icmp_msgs_per_sec */
- if (!icmpv4_global_allow(net, type, code))
+ /* is global icmp_msgs_per_sec exhausted ? */
+ if (!icmpv4_global_allow(net, type, code, &apply_ratelimit))
goto out_bh_enable;
sk = icmp_xmit_lock(net);
@@ -450,7 +458,7 @@ static void icmp_reply(struct icmp_bxm *icmp_param, struct sk_buff *skb)
rt = ip_route_output_key(net, &fl4);
if (IS_ERR(rt))
goto out_unlock;
- if (icmpv4_xrlim_allow(net, rt, &fl4, type, code))
+ if (icmpv4_xrlim_allow(net, rt, &fl4, type, code, apply_ratelimit))
icmp_push_reply(sk, icmp_param, &fl4, &ipc, &rt);
ip_rt_put(rt);
out_unlock:
@@ -596,6 +604,7 @@ void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
int room;
struct icmp_bxm icmp_param;
struct rtable *rt = skb_rtable(skb_in);
+ bool apply_ratelimit = false;
struct ipcm_cookie ipc;
struct flowi4 fl4;
__be32 saddr;
@@ -677,7 +686,7 @@ void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
}
}
- /* Needed by both icmp_global_allow and icmp_xmit_lock */
+ /* Needed by both icmpv4_global_allow and icmp_xmit_lock */
local_bh_disable();
/* Check global sysctl_icmp_msgs_per_sec ratelimit, unless
@@ -685,7 +694,7 @@ void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
* loopback, then peer ratelimit still work (in icmpv4_xrlim_allow)
*/
if (!(skb_in->dev && (skb_in->dev->flags&IFF_LOOPBACK)) &&
- !icmpv4_global_allow(net, type, code))
+ !icmpv4_global_allow(net, type, code, &apply_ratelimit))
goto out_bh_enable;
sk = icmp_xmit_lock(net);
@@ -744,7 +753,7 @@ void __icmp_send(struct sk_buff *skb_in, int type, int code, __be32 info,
goto out_unlock;
/* peer icmp_ratelimit */
- if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code))
+ if (!icmpv4_xrlim_allow(net, rt, &fl4, type, code, apply_ratelimit))
goto ende;
/* RFC says return as much as we can without exceeding 576 bytes. */
diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index 7b31674644efc338ec458d92dfe495480825b0fd..46f70e4a835139ef7d8925c49440865355048193 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -175,14 +175,16 @@ static bool icmpv6_mask_allow(struct net *net, int type)
return false;
}
-static bool icmpv6_global_allow(struct net *net, int type)
+static bool icmpv6_global_allow(struct net *net, int type,
+ bool *apply_ratelimit)
{
if (icmpv6_mask_allow(net, type))
return true;
- if (icmp_global_allow())
+ if (icmp_global_allow()) {
+ *apply_ratelimit = true;
return true;
-
+ }
__ICMP_INC_STATS(net, ICMP_MIB_RATELIMITGLOBAL);
return false;
}
@@ -191,13 +193,13 @@ static bool icmpv6_global_allow(struct net *net, int type)
* Check the ICMP output rate limit
*/
static bool icmpv6_xrlim_allow(struct sock *sk, u8 type,
- struct flowi6 *fl6)
+ struct flowi6 *fl6, bool apply_ratelimit)
{
struct net *net = sock_net(sk);
struct dst_entry *dst;
bool res = false;
- if (icmpv6_mask_allow(net, type))
+ if (!apply_ratelimit)
return true;
/*
@@ -228,6 +230,8 @@ static bool icmpv6_xrlim_allow(struct sock *sk, u8 type,
if (!res)
__ICMP6_INC_STATS(net, ip6_dst_idev(dst),
ICMP6_MIB_RATELIMITHOST);
+ else
+ icmp_global_consume();
dst_release(dst);
return res;
}
@@ -452,6 +456,7 @@ void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
struct net *net;
struct ipv6_pinfo *np;
const struct in6_addr *saddr = NULL;
+ bool apply_ratelimit = false;
struct dst_entry *dst;
struct icmp6hdr tmp_hdr;
struct flowi6 fl6;
@@ -533,11 +538,12 @@ void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
return;
}
- /* Needed by both icmp_global_allow and icmpv6_xmit_lock */
+ /* Needed by both icmpv6_global_allow and icmpv6_xmit_lock */
local_bh_disable();
/* Check global sysctl_icmp_msgs_per_sec ratelimit */
- if (!(skb->dev->flags & IFF_LOOPBACK) && !icmpv6_global_allow(net, type))
+ if (!(skb->dev->flags & IFF_LOOPBACK) &&
+ !icmpv6_global_allow(net, type, &apply_ratelimit))
goto out_bh_enable;
mip6_addr_swap(skb, parm);
@@ -575,7 +581,7 @@ void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
np = inet6_sk(sk);
- if (!icmpv6_xrlim_allow(sk, type, &fl6))
+ if (!icmpv6_xrlim_allow(sk, type, &fl6, apply_ratelimit))
goto out;
tmp_hdr.icmp6_type = type;
@@ -717,6 +723,7 @@ static enum skb_drop_reason icmpv6_echo_reply(struct sk_buff *skb)
struct ipv6_pinfo *np;
const struct in6_addr *saddr = NULL;
struct icmp6hdr *icmph = icmp6_hdr(skb);
+ bool apply_ratelimit = false;
struct icmp6hdr tmp_hdr;
struct flowi6 fl6;
struct icmpv6_msg msg;
@@ -781,8 +788,9 @@ static enum skb_drop_reason icmpv6_echo_reply(struct sk_buff *skb)
goto out;
/* Check the ratelimit */
- if ((!(skb->dev->flags & IFF_LOOPBACK) && !icmpv6_global_allow(net, ICMPV6_ECHO_REPLY)) ||
- !icmpv6_xrlim_allow(sk, ICMPV6_ECHO_REPLY, &fl6))
+ if ((!(skb->dev->flags & IFF_LOOPBACK) &&
+ !icmpv6_global_allow(net, ICMPV6_ECHO_REPLY, &apply_ratelimit)) ||
+ !icmpv6_xrlim_allow(sk, ICMPV6_ECHO_REPLY, &fl6, apply_ratelimit))
goto out_dst_release;
idev = __in6_dev_get(skb->dev);
--
2.46.0.295.g3b9ea8a38a-goog
