In the Linux kernel, the following vulnerability has been resolved:
vlan: fix skb_under_panic and races when toggling HW VLAN offload
Toggling hardware VLAN TX offload (NETIF_F_HW_VLAN_CTAG_TX or
NETIF_F_HW_VLAN_STAG_TX) on a lower device invokes vlan_transfer_features(),
which dynamically changed vlandev->hard_header_len.
This causes two issues:
1. Lockless TX paths (e.g. packet_snd in af_packet.c, ip6_finish_output2)
read dev->hard_header_len without holding RTNL lock. Mutating
hard_header_len dynamically under RTNL creates a data race where upper
layers reserve insufficient headroom based on a stale hard_header_len,
resulting in skb_under_panic when vlan_dev_hard_header() is called.
2. In addition, vlan_transfer_features() updated hard_header_len without
updating header_ops, causing a mismatch between allocated headroom
and header creation.
Always setting dev->hard_header_len = real_dev->hard_header_len and
dev->needed_headroom = real_dev->needed_headroom + VLAN_HLEN unconditionally
ensures:
- dev->hard_header_len remains 100% static and immutable at real_dev->hard_header_len,
eliminating all dynamic runtime updates and data races on hard_header_len.
- Upper layers allocating skbs via LL_RESERVED_SPACE() will always reserve
sufficient headroom for software VLAN tag insertion (real_dev->hard_header_len +
real_dev->needed_headroom + VLAN_HLEN).
- vlandev inherits real_dev->needed_tailroom so underlying trailer/padding/ICV
requirements are honored.
- AF_PACKET SOCK_RAW network header offsets remain correctly aligned at
real_dev->hard_header_len.
- vlan_header_ops is used unconditionally.
Note to stable teams: Make sure to backport these commits:
e16e960d55a4 ("ipvlan: inherit needed_headroom and needed_tailroom from phy_dev")
cef51860becd ("macvlan: inherit needed_headroom and needed_tailroom from lowerdev")
vlan: fix skb_under_panic and races when toggling HW VLAN offload
Toggling hardware VLAN TX offload (NETIF_F_HW_VLAN_CTAG_TX or
NETIF_F_HW_VLAN_STAG_TX) on a lower device invokes vlan_transfer_features(),
which dynamically changed vlandev->hard_header_len.
This causes two issues:
1. Lockless TX paths (e.g. packet_snd in af_packet.c, ip6_finish_output2)
read dev->hard_header_len without holding RTNL lock. Mutating
hard_header_len dynamically under RTNL creates a data race where upper
layers reserve insufficient headroom based on a stale hard_header_len,
resulting in skb_under_panic when vlan_dev_hard_header() is called.
2. In addition, vlan_transfer_features() updated hard_header_len without
updating header_ops, causing a mismatch between allocated headroom
and header creation.
Always setting dev->hard_header_len = real_dev->hard_header_len and
dev->needed_headroom = real_dev->needed_headroom + VLAN_HLEN unconditionally
ensures:
- dev->hard_header_len remains 100% static and immutable at real_dev->hard_header_len,
eliminating all dynamic runtime updates and data races on hard_header_len.
- Upper layers allocating skbs via LL_RESERVED_SPACE() will always reserve
sufficient headroom for software VLAN tag insertion (real_dev->hard_header_len +
real_dev->needed_headroom + VLAN_HLEN).
- vlandev inherits real_dev->needed_tailroom so underlying trailer/padding/ICV
requirements are honored.
- AF_PACKET SOCK_RAW network header offsets remain correctly aligned at
real_dev->hard_header_len.
- vlan_header_ops is used unconditionally.
Note to stable teams: Make sure to backport these commits:
e16e960d55a4 ("ipvlan: inherit needed_headroom and needed_tailroom from phy_dev")
cef51860becd ("macvlan: inherit needed_headroom and needed_tailroom from lowerdev")
Default status is the baseline for the product, each version can override it (e.g. patched versions marked unaffected).
| Vendor | Product | Default status | Versions | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Linux | Linux | unaffected |
|
|||||||||||||||
| Linux | Linux | affected |
|
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Advisories
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Fixes
Solution
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Workaround
No workaround given by the vendor.
References
History
Wed, 09 Sep 2026 16:30:00 +0000
| Type | Values Removed | Values Added |
|---|---|---|
| Description | In the Linux kernel, the following vulnerability has been resolved: vlan: fix skb_under_panic and races when toggling HW VLAN offload Toggling hardware VLAN TX offload (NETIF_F_HW_VLAN_CTAG_TX or NETIF_F_HW_VLAN_STAG_TX) on a lower device invokes vlan_transfer_features(), which dynamically changed vlandev->hard_header_len. This causes two issues: 1. Lockless TX paths (e.g. packet_snd in af_packet.c, ip6_finish_output2) read dev->hard_header_len without holding RTNL lock. Mutating hard_header_len dynamically under RTNL creates a data race where upper layers reserve insufficient headroom based on a stale hard_header_len, resulting in skb_under_panic when vlan_dev_hard_header() is called. 2. In addition, vlan_transfer_features() updated hard_header_len without updating header_ops, causing a mismatch between allocated headroom and header creation. Always setting dev->hard_header_len = real_dev->hard_header_len and dev->needed_headroom = real_dev->needed_headroom + VLAN_HLEN unconditionally ensures: - dev->hard_header_len remains 100% static and immutable at real_dev->hard_header_len, eliminating all dynamic runtime updates and data races on hard_header_len. - Upper layers allocating skbs via LL_RESERVED_SPACE() will always reserve sufficient headroom for software VLAN tag insertion (real_dev->hard_header_len + real_dev->needed_headroom + VLAN_HLEN). - vlandev inherits real_dev->needed_tailroom so underlying trailer/padding/ICV requirements are honored. - AF_PACKET SOCK_RAW network header offsets remain correctly aligned at real_dev->hard_header_len. - vlan_header_ops is used unconditionally. Note to stable teams: Make sure to backport these commits: e16e960d55a4 ("ipvlan: inherit needed_headroom and needed_tailroom from phy_dev") cef51860becd ("macvlan: inherit needed_headroom and needed_tailroom from lowerdev") | |
| Title | vlan: fix skb_under_panic and races when toggling HW VLAN offload | |
| First Time appeared |
Linux
Linux linux Kernel |
|
| CPEs | cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | |
| Vendors & Products |
Linux
Linux linux Kernel |
|
| References |
|
Projects
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MITRE
Status: PUBLISHED
Assigner: Linux
Published:
Updated: 2026-09-09T16:19:44.748Z
Reserved: 2026-08-26T14:34:25.802Z
Link: CVE-2026-80925
Vulnrichment
No data.
NVD
Status : Received
Published: 2026-09-09T17:17:47.763
Modified: 2026-09-09T17:17:47.763
Link: CVE-2026-80925
Redhat
No data.
OpenCVE Enrichment
No data.
Weaknesses
No weakness.