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net: Preserve metadata on pskb_expand_head

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pskb_expand_head() copies headroom, including skb metadata, into the newly
allocated head, but then clears the metadata. As a result, metadata is lost
when BPF helpers trigger an skb head reallocation.

Let the skb metadata remain in the newly created copy of head.

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-v4-2-5ceb08a9b37b@cloudflare.com
This commit is contained in:
Jakub Sitnicki
2025-11-05 21:19:39 +01:00
committed by Martin KaFai Lau
parent 8989d328df
commit 290fc0be09
1 changed files with 4 additions and 2 deletions
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6
net/core/skbuff.c
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@@ -2234,6 +2234,10 @@ EXPORT_SYMBOL(__pskb_copy_fclone);
*
* All the pointers pointing into skb header may change and must be
* reloaded after call to this function.
*
* Note: If you skb_push() the start of the buffer after reallocating the
* header, call skb_postpush_data_move() first to move the metadata out of
* the way before writing to &sk_buff->data.
*/
int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
@@ -2305,8 +2309,6 @@ int pskb_expand_head(struct sk_buff *skb, int nhead, int ntail,
skb->nohdr = 0;
atomic_set(&skb_shinfo(skb)->dataref, 1);
skb_metadata_clear(skb);
/* It is not generally safe to change skb->truesize.
* For the moment, we really care of rx path, or
* when skb is orphaned (not attached to a socket).