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bpf: Unclone skb head on bpf_dynptr_write to skb metadata

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Currently bpf_dynptr_from_skb_meta() marks the dynptr as read-only when
the skb is cloned, preventing writes to metadata.

Remove this restriction and unclone the skb head on bpf_dynptr_write() to
metadata, now that the metadata is preserved during uncloning. This makes
metadata dynptr consistent with skb dynptr, allowing writes regardless of
whether the skb is cloned.

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-v4-3-5ceb08a9b37b@cloudflare.com
This commit is contained in:
Jakub Sitnicki
2025-11-05 21:19:40 +01:00
committed by Martin KaFai Lau
parent 290fc0be09
commit f38499ff45
3 changed files with 23 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
kernel/bpf/helpers.c
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@@ -1842,10 +1842,8 @@ int __bpf_dynptr_write(const struct bpf_dynptr_kern *dst, u32 offset, void *src,
return -EINVAL;
return __bpf_xdp_store_bytes(dst->data, dst->offset + offset, src, len);
case BPF_DYNPTR_TYPE_SKB_META:
if (flags)
return -EINVAL;
memmove(bpf_skb_meta_pointer(dst->data, dst->offset + offset), src, len);
return 0;
return __bpf_skb_meta_store_bytes(dst->data, dst->offset + offset, src,
len, flags);
default:
WARN_ONCE(true, "bpf_dynptr_write: unknown dynptr type %d\n", type);
return -EFAULT;