Commit 290fc0be authored by Jakub Sitnicki's avatar Jakub Sitnicki Committed by Martin KaFai Lau
Browse files

net: Preserve metadata on pskb_expand_head 



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: default avatarJakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: default avatarMartin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20251105-skb-meta-rx-path-v4-2-5ceb08a9b37b@cloudflare.com
parent 8989d328

net/core/skbuff.c

+4 −2
Original line number Diff line number Diff line
@@ -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).