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 --- net/core/skbuff.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-) diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 6be01454f262..b4fa9aa2df22 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -2218,6 +2218,10 @@ 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, @@ -2289,8 +2293,6 @@ 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). -- 2.43.0