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

[Nicolai Buchwitz <nb@tipi-net.de>]

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.

Signed-off-by: Nicolai Buchwitz <nb@tipi-net.de>
---
Nicolai Buchwitz (3):
      net: selftests: use skb_share_check() in the loopback receive hook
      net: stmmac: selftests: use skb_share_check() in the loopback receive hook
      net/mlx5e: use skb_share_check() in the loopback selftest hook

 drivers/net/ethernet/mellanox/mlx5/core/en_selftest.c  | 4 ++++
 drivers/net/ethernet/stmicro/stmmac/stmmac_selftests.c | 2 +-
 net/core/selftests.c                                   | 2 +-
 3 files changed, 6 insertions(+), 2 deletions(-)
---
base-commit: 45ad84d2800e4a092fb8d96006a533b2d0ab13f6
change-id: 20261007-nb-net-selftest-shared-net-823dc91ed5bf

Best regards,
--  
Nicolai Buchwitz <nb@tipi-net.de>