can: dev: init_can_skb(): restore skb header initialization

Overview

In the Linux kernel, the following vulnerability has been resolved:

can: dev: init_can_skb(): restore skb header initialization

Commit 9f10374bb024 ("can: remove private CAN skb headroom infrastructure") removed the skb_reset_mac_header()/skb_reset_network_header()/ skb_reset_transport_header() calls from init_can_skb(). As a result, RX skbs from alloc_can_skb() and friends again carry mac_header = 0xFFFF. When such an skb reaches packet_rcv_spkt() (SOCK_PACKET), the push length calculation overflows and triggers skb_under_panic -> kernel BUG -> full machine panic.

The same issue was originally reported in 2014 on linux-can and fixed by commit 969439016d2c ("can: add missing initialisations in CAN related skbuffs"). packet_rcv_spkt() itself has never been hardened: only packet_rcv() and tpacket_rcv() gained dev_has_header() checks in commit d549699048b4 ("net/packet: fix packet receive on L3 devices without visible hard header").

Affected

• Linux >= 9f10374bb024593a611e6845847f0444841a231b < 8078375dfd0baecd9f1b7b06bb2d6f88d7cb8632
• Linux >= 9f10374bb024593a611e6845847f0444841a231b < 0a04c0cb8606ff88399489d03ef255afe90d0d5f
• Linux 7.0

Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.