Linux vulnerability

What happened

In the Linux kernel, the following vulnerability has been resolved: net: cap advertised IP tunnel headroom IP tunnel devices derive their advertised needed_headroom from lower output devices. A stack of user-created devices can make the derived value larger than the 16-bit skb header offsets can represent. Once IP output reserves it, skb head expansion can wrap those offsets. The runtime transmit path already caps a growing needed_headroom at 512. Apply the same cap when tunnel configuration publishes needed_headroom derived from a lower output device. Capping the advertised value is safe: IP tunnel transmit still expands the skb when a packet needs more headroom. A nonsensical stacked configuration can therefore incur an extra reallocation, but it cannot publish an unbounded reservation to upper layers.

Affected versions

Linux: 1a37e412a0225fcba5587f24c0dfc7636efc8b69 through before bc4e05ae66c9797a0972ac44326e69c5305e0020 (git); 1a37e412a0225fcba5587f24c0dfc7636efc8b69 through before af0ee8f04bea22cdb331fa3509e17f81b48938ad (git); 1a37e412a0225fcba5587f24c0dfc7636efc8b69 through before 9144f2c53a04465a6878172b523f640313c5559e (git); 1a37e412a0225fcba5587f24c0dfc7636efc8b69 through before 6b222adeb9340306e2ff97127c76117abb9b3df8 (git); 3.11 Fixed: See vendor advisory.

Why it matters

Review the vendor advisory and exposure of the affected product to determine operational impact.

Detection & mitigation

• Apply vendor-provided updates or mitigations.
• Review affected product exposure and access logs.