[PATCH net-next 0/3] net: use skb_share_check() in loopback selftest hooks

[Jakub Kicinski]

On Wed, 07 Oct 2026 20:29:21 +0200 Nicolai Buchwitz wrote:
> The loopback selftest hooks can get a shared skb when another handler
> is bound to the device. Linearizing a non-linear frame then hits
> BUG_ON(skb_shared()) in pskb_expand_head().
> 
> Stumbled over this on RPi CM4 (bcmgenet, with jumbo series applied +
> WIP selftest patches) with a packet socket open at the same time as
> running ethtool -t.
> 
> stmmac and mlx5 seem to have the same pattern, xgbe already handles
> shared skbs. Patches 2 and 3 are compile tested only.
> 
> As the impact is pretty limited and doesn't seem to bother anyone in
> the wild, I've chosen net-next, but kept the Fixes tags. That matches
> what Paolo suggested during the LPC track.

Wonder if we should follow up and rename skb_unshare to skb_unclone_full
or some such? The "share" in the name is quite confusing for people who
haven't been around for 10+ years..