[PATCH v4 net 0/2] net: vlan: fix skb_panic bug in vlan_dev_hard_header()

[Chen Zhen <chenzhen126@huawei.com>]

This series fix a skb_panic bug in vlan_dev_hard_header().

If a vlan device with reorder_hdr off is created without hw offload
feature, but up with hw offload on, the ndisc skb has no enough
room for vlan hdr in vlan_dev_hard_header() and finally panic.

The first patch fixes the bug itself by always set hard_header_len with
VLAN_HLEN. The second patch adds a regression test for this bug.

---
v3 -> v4:
- Change the fix method to cover other callers as suggested by Eric, thx!
- v3: https://lore.kernel.org/all/20260112075939.2509397-1-chenzhen126@huawei.com/

v2 -> v3:
- Add a comment to test script to silence shellcheck SC2329 warning
- v2: https://lore.kernel.org/all/20260107033423.1885071-1-chenzhen126@huawei.com/

v1 -> v2:
- Address format issues of commit message
- Add a selftest to catch re-occurrence of this issue as suggested by Jakub
- v1: https://lore.kernel.org/all/20251231035419.23422-1-chenzhen126@huawei.com/

Chen Zhen (2):
  net: vlan: always set hard_header_len with VLAN_HLEN
  selftests: vlan: add test for turn on hw offload with reorder_hdr off

 net/8021q/vlan.c                              |  5 ---
 net/8021q/vlan_dev.c                          |  8 ++---
 tools/testing/selftests/net/Makefile          |  1 +
 .../testing/selftests/net/vlan_hw_offload.sh  | 31 +++++++++++++++++++
 4 files changed, 35 insertions(+), 10 deletions(-)
 create mode 100755 tools/testing/selftests/net/vlan_hw_offload.sh

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2.33.0