With the introduction of bpf_dynptr_from_skb_meta, all BPF programs authorized to call skb kfuncs (bpf_kfunc_set_skb) now have access to the skb metadata area. These programs can read up to skb_shinfo(skb)->meta_len bytes located just before skb_mac_header(skb), regardless of what data is currently there. However, as the network stack processes the skb, headers may be added or removed. Hence, we cannot assume that skb_mac_header() always marks the end of the metadata area. To avoid potential pitfalls, reset the skb metadata length to zero before passing the skb to the protocol layers. This is a temporary measure until we can make metadata persist through protocol processing. The change is backward compatible as today only TC BPF programs can access skb metadata through the __sk_buff->data_meta pointer. Signed-off-by: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx> --- net/core/dev.c | 1 + 1 file changed, 1 insertion(+) diff --git a/net/core/dev.c b/net/core/dev.c index 7969fddc94e3..6546ee7c3799 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -5839,6 +5839,7 @@ static int __netif_receive_skb_core(struct sk_buff **pskb, bool pfmemalloc, } #endif skb_reset_redirect(skb); + skb_metadata_clear(skb); skip_classify: if (pfmemalloc && !skb_pfmemalloc_protocol(skb)) goto drop; -- 2.43.0
