@@ -1498,7 +1498,7 @@ __skb_set_sw_hash(struct sk_buff *skb, __u32 hash, bool is_l4)
__skb_set_hash(skb, hash, true, is_l4);
}
-void __skb_get_hash(struct sk_buff *skb);
+void __skb_get_hash_net(const struct net *net, struct sk_buff *skb);
u32 __skb_get_hash_symmetric(const struct sk_buff *skb);
u32 skb_get_poff(const struct sk_buff *skb);
u32 __skb_get_poff(const struct sk_buff *skb, const void *data,
@@ -1578,10 +1578,18 @@ void skb_flow_dissect_hash(const struct sk_buff *skb,
struct flow_dissector *flow_dissector,
void *target_container);
+static inline __u32 skb_get_hash_net(const struct net *net, struct sk_buff *skb)
+{
+ if (!skb->l4_hash && !skb->sw_hash)
+ __skb_get_hash_net(net, skb);
+
+ return skb->hash;
+}
+
static inline __u32 skb_get_hash(struct sk_buff *skb)
{
if (!skb->l4_hash && !skb->sw_hash)
- __skb_get_hash(skb);
+ __skb_get_hash_net(NULL, skb);
return skb->hash;
}
@@ -1860,7 +1860,8 @@ u32 __skb_get_hash_symmetric(const struct sk_buff *skb)
EXPORT_SYMBOL_GPL(__skb_get_hash_symmetric);
/**
- * __skb_get_hash: calculate a flow hash
+ * __skb_get_hash_net: calculate a flow hash
+ * @net: associated network namespace, derived from @skb if NULL
* @skb: sk_buff to calculate flow hash from
*
* This function calculates a flow hash based on src/dst addresses
@@ -1868,18 +1869,24 @@ EXPORT_SYMBOL_GPL(__skb_get_hash_symmetric);
* on success, zero indicates no valid hash. Also, sets l4_hash in skb
* if hash is a canonical 4-tuple hash over transport ports.
*/
-void __skb_get_hash(struct sk_buff *skb)
+void __skb_get_hash_net(const struct net *net, struct sk_buff *skb)
{
struct flow_keys keys;
u32 hash;
+ memset(&keys, 0, sizeof(keys));
+
+ __skb_flow_dissect(net, skb, &flow_keys_dissector,
+ &keys, NULL, 0, 0, 0,
+ FLOW_DISSECTOR_F_STOP_AT_FLOW_LABEL);
+
__flow_hash_secret_init();
- hash = ___skb_get_hash(skb, &keys, &hashrnd);
+ hash = __flow_hash_from_keys(&keys, &hashrnd);
__skb_set_sw_hash(skb, hash, flow_keys_have_l4(&keys));
}
-EXPORT_SYMBOL(__skb_get_hash);
+EXPORT_SYMBOL(__skb_get_hash_net);
__u32 skb_get_hash_perturb(const struct sk_buff *skb,
const siphash_key_t *perturb)
@@ -317,7 +317,7 @@ void nft_trace_init(struct nft_traceinfo *info, const struct nft_pktinfo *pkt,
net_get_random_once(&trace_key, sizeof(trace_key));
info->skbid = (u32)siphash_3u32(hash32_ptr(skb),
- skb_get_hash(skb),
+ skb_get_hash_net(nft_net(pkt), skb),
skb->skb_iif,
&trace_key);
}
Years ago flow dissector gained ability to delegate flow dissection to a bpf program, scoped per netns. Unfortunately, skb_get_hash() only gets an sk_buff argument instead of both net+skb. This means the flow dissector needs to obtain the netns pointer from somewhere else. The netns is derived from skb->dev, and if that is not available, from skb->sk. If neither is set, we hit a (benign) WARN_ON_ONCE(). Trying both dev and sk covers most cases, but not all, as recently reported by Christoph Paasch. In case of nf-generated tcp reset, both sk and dev are NULL: WARNING: .. net/core/flow_dissector.c:1104 skb_flow_dissect_flow_keys include/linux/skbuff.h:1536 [inline] skb_get_hash include/linux/skbuff.h:1578 [inline] nft_trace_init+0x7d/0x120 net/netfilter/nf_tables_trace.c:320 nft_do_chain+0xb26/0xb90 net/netfilter/nf_tables_core.c:268 nft_do_chain_ipv4+0x7a/0xa0 net/netfilter/nft_chain_filter.c:23 nf_hook_slow+0x57/0x160 net/netfilter/core.c:626 __ip_local_out+0x21d/0x260 net/ipv4/ip_output.c:118 ip_local_out+0x26/0x1e0 net/ipv4/ip_output.c:127 nf_send_reset+0x58c/0x700 net/ipv4/netfilter/nf_reject_ipv4.c:308 nft_reject_ipv4_eval+0x53/0x90 net/ipv4/netfilter/nft_reject_ipv4.c:30 [..] syzkaller did something like this: table inet filter { chain input { type filter hook input priority filter; policy accept; meta nftrace set 1 tcp dport 42 reject with tcp reset } chain output { type filter hook output priority filter; policy accept; # empty chain is enough } } ... then sends a tcp packet to port 42. Initial attempt to simply set skb->dev from nf_reject_ipv4 doesn't cover all cases: skbs generated via ipv4 igmp_send_report trigger similar splat. Moreover, Pablo Neira found that nft_hash.c uses __skb_get_hash_symmetric() which would trigger same warn splat for such skbs. Lets allow callers to pass the current netns explicitly. The nf_trace infrastructure is adjusted to use the new helper. __skb_get_hash_symmetric is handled in the next patch. Reported-by: Christoph Paasch <cpaasch@apple.com> Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/494 Reviewed-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Willem de Bruijn <willemb@google.com> Signed-off-by: Florian Westphal <fw@strlen.de> --- Changes since v1: add @net to kdoc comment (kbuild robot warning), no other changes. include/linux/skbuff.h | 12 ++++++++++-- net/core/flow_dissector.c | 15 +++++++++++---- net/netfilter/nf_tables_trace.c | 2 +- 3 files changed, 22 insertions(+), 7 deletions(-)