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authorDaniel Borkmann <daniel@iogearbox.net>2016-06-10 21:19:06 +0200
committerDavid S. Miller <davem@davemloft.net>2016-06-10 18:00:57 -0700
commita70b506efe899dc8d650eafcc0b11fc9ee746627 (patch)
treee938bd0ddcc06c32df59b527d148ffa7aab9f636 /net/core
parentf2a4d086ed4c588d32fe9b7aa67fead7280e7bf1 (diff)
bpf: enforce recursion limit on redirects
Respect the stack's xmit_recursion limit for calls into dev_queue_xmit(). Currently, they are not handeled by the limiter when attached to clsact's egress parent, for example, and a buggy program redirecting it to the same device again could run into stack overflow eventually. It would be good if we could notify an admin to give him a chance to react. We reuse xmit_recursion instead of having one private to eBPF, so that the stack's current recursion depth will be taken into account as well. Follow-up to commit 3896d655f4d4 ("bpf: introduce bpf_clone_redirect() helper") and 27b29f63058d ("bpf: add bpf_redirect() helper"). Signed-off-by: Daniel Borkmann <daniel@iogearbox.net> Acked-by: Alexei Starovoitov <ast@kernel.org> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core')
-rw-r--r--net/core/dev.c6
-rw-r--r--net/core/filter.c55
2 files changed, 36 insertions, 25 deletions
diff --git a/net/core/dev.c b/net/core/dev.c
index c43c9d2a88cf..b14835757141 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3144,8 +3144,6 @@ static void skb_update_prio(struct sk_buff *skb)
DEFINE_PER_CPU(int, xmit_recursion);
EXPORT_SYMBOL(xmit_recursion);
-#define RECURSION_LIMIT 10
-
/**
* dev_loopback_xmit - loop back @skb
* @net: network namespace this loopback is happening in
@@ -3388,8 +3386,8 @@ static int __dev_queue_xmit(struct sk_buff *skb, void *accel_priv)
int cpu = smp_processor_id(); /* ok because BHs are off */
if (txq->xmit_lock_owner != cpu) {
-
- if (__this_cpu_read(xmit_recursion) > RECURSION_LIMIT)
+ if (unlikely(__this_cpu_read(xmit_recursion) >
+ XMIT_RECURSION_LIMIT))
goto recursion_alert;
skb = validate_xmit_skb(skb, dev);
diff --git a/net/core/filter.c b/net/core/filter.c
index 68adb5f52110..d11744d10e00 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1603,9 +1603,36 @@ static const struct bpf_func_proto bpf_csum_diff_proto = {
.arg5_type = ARG_ANYTHING,
};
+static inline int __bpf_rx_skb(struct net_device *dev, struct sk_buff *skb)
+{
+ if (skb_at_tc_ingress(skb))
+ skb_postpush_rcsum(skb, skb_mac_header(skb), skb->mac_len);
+
+ return dev_forward_skb(dev, skb);
+}
+
+static inline int __bpf_tx_skb(struct net_device *dev, struct sk_buff *skb)
+{
+ int ret;
+
+ if (unlikely(__this_cpu_read(xmit_recursion) > XMIT_RECURSION_LIMIT)) {
+ net_crit_ratelimited("bpf: recursion limit reached on datapath, buggy bpf program?\n");
+ kfree_skb(skb);
+ return -ENETDOWN;
+ }
+
+ skb->dev = dev;
+
+ __this_cpu_inc(xmit_recursion);
+ ret = dev_queue_xmit(skb);
+ __this_cpu_dec(xmit_recursion);
+
+ return ret;
+}
+
static u64 bpf_clone_redirect(u64 r1, u64 ifindex, u64 flags, u64 r4, u64 r5)
{
- struct sk_buff *skb = (struct sk_buff *) (long) r1, *skb2;
+ struct sk_buff *skb = (struct sk_buff *) (long) r1;
struct net_device *dev;
if (unlikely(flags & ~(BPF_F_INGRESS)))
@@ -1615,19 +1642,12 @@ static u64 bpf_clone_redirect(u64 r1, u64 ifindex, u64 flags, u64 r4, u64 r5)
if (unlikely(!dev))
return -EINVAL;
- skb2 = skb_clone(skb, GFP_ATOMIC);
- if (unlikely(!skb2))
+ skb = skb_clone(skb, GFP_ATOMIC);
+ if (unlikely(!skb))
return -ENOMEM;
- if (flags & BPF_F_INGRESS) {
- if (skb_at_tc_ingress(skb2))
- skb_postpush_rcsum(skb2, skb_mac_header(skb2),
- skb2->mac_len);
- return dev_forward_skb(dev, skb2);
- }
-
- skb2->dev = dev;
- return dev_queue_xmit(skb2);
+ return flags & BPF_F_INGRESS ?
+ __bpf_rx_skb(dev, skb) : __bpf_tx_skb(dev, skb);
}
static const struct bpf_func_proto bpf_clone_redirect_proto = {
@@ -1671,15 +1691,8 @@ int skb_do_redirect(struct sk_buff *skb)
return -EINVAL;
}
- if (ri->flags & BPF_F_INGRESS) {
- if (skb_at_tc_ingress(skb))
- skb_postpush_rcsum(skb, skb_mac_header(skb),
- skb->mac_len);
- return dev_forward_skb(dev, skb);
- }
-
- skb->dev = dev;
- return dev_queue_xmit(skb);
+ return ri->flags & BPF_F_INGRESS ?
+ __bpf_rx_skb(dev, skb) : __bpf_tx_skb(dev, skb);
}
static const struct bpf_func_proto bpf_redirect_proto = {