Linux vulnerability

What happened

In the Linux kernel, the following vulnerability has been resolved: net: tun: bound receive headroom tun_get_user() uses tun->align both as skb headroom and when choosing how much packet data to keep linear. OVS can propagate an oversized headroom request from another port to TUN or TAP. When align is larger than the usable space in a one-page skb head, SKB_MAX_HEAD(align) underflows and the result becomes negative when stored in good_linear. That value later wraps when assigned to the size_t linear variable, and tun_alloc_skb() can place skb->data outside the allocated head. Bound the headroom stored by TUN to the one-page skb-head budget and the largest non-sentinel 16-bit skb header offset. Leave one linear byte for raw TUN and a complete Ethernet header for TAP, including NET_IP_ALIGN. Also pull the raw-TUN protocol byte and the TAP Ethernet header before accessing them, so these checks remain safe for nonlinear skbs supplied by other allocation paths.

Affected versions

Linux: eaea34b23c46bf17b4a5638be69ab3561854f34b through before 379d85c7f25f3e05a428225e6b8a65613c6e9b9d (git); eaea34b23c46bf17b4a5638be69ab3561854f34b through before e098d9cc8859614a7f7baebc96e32a5a16b18ed2 (git); eaea34b23c46bf17b4a5638be69ab3561854f34b through before 0ada54ea63e48b9c1608e917ccb7dfadbe86db28 (git); eaea34b23c46bf17b4a5638be69ab3561854f34b through before 447c9303942c439a117d9b76ce6d6e2116b38ee7 (git); 4.6 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.