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bpf: Make bpf_skb_change_head helper metadata-safe

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Although bpf_skb_change_head() doesn't move packet data after skb_push(),
skb metadata still needs to be relocated. Use the dedicated helper to
handle it.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20251105-skb-meta-rx-path-v4-9-5ceb08a9b37b@cloudflare.com
This commit is contained in:
Jakub Sitnicki 2025-11-05 21:19:46 +01:00 committed by Martin KaFai Lau
parent 8cfc172ce2
commit fb206fc312
1 changed files with 3 additions and 1 deletions
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4
net/core/filter.c
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@ -3875,6 +3875,7 @@ static const struct bpf_func_proto sk_skb_change_tail_proto = {
static inline int __bpf_skb_change_head(struct sk_buff *skb, u32 head_room,
u64 flags)
{
const u8 meta_len = skb_metadata_len(skb);
u32 max_len = BPF_SKB_MAX_LEN;
u32 new_len = skb->len + head_room;
int ret;
@ -3884,7 +3885,7 @@ static inline int __bpf_skb_change_head(struct sk_buff *skb, u32 head_room,
new_len < skb->len))
return -EINVAL;
ret = skb_cow(skb, head_room);
ret = skb_cow(skb, meta_len + head_room);
if (likely(!ret)) {
/* Idea for this helper is that we currently only
* allow to expand on mac header. This means that
@ -3896,6 +3897,7 @@ static inline int __bpf_skb_change_head(struct sk_buff *skb, u32 head_room,
* for redirection into L2 device.
*/
__skb_push(skb, head_room);
skb_postpush_data_move(skb, head_room, 0);
memset(skb->data, 0, head_room);
skb_reset_mac_header(skb);
skb_reset_mac_len(skb);