CVE-2021-47293

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

net/sched: act_skbmod: Skip non-Ethernet packets

Currently tcf_skbmod_act() assumes that packets use Ethernet as their L2 protocol, which is not always the case. As an example, for CAN devices:

$ ip link add dev vcan0 type vcan
$ ip link set up vcan0
$ tc qdisc add dev vcan0 root handle 1: htb
$ tc filter add dev vcan0 parent 1: protocol ip prio 10 
	matchall action skbmod swap mac

Doing the above silently corrupts all the packets. Do not perform skbmod actions for non-Ethernet packets.

Affected Software

References

• https://git.kernel.org/stable/c/071729150be9e1d1b851b70efb6d91ee9269d57b
• https://git.kernel.org/stable/c/34f1e1f657fae2891b485a3b2b95fe4d2aef9f0d
• https://git.kernel.org/stable/c/727d6a8b7ef3d25080fad228b2c4a1d4da5999c6
• https://git.kernel.org/stable/c/a88414fb1117f2fe65fb88e45ba694e1d09d5024
• https://git.kernel.org/stable/c/e4fdca366806f6bab374d1a95e626a10a3854b0c