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Commit a88414fb authored by Peilin Ye's avatar Peilin Ye Committed by Greg Kroah-Hartman
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net/sched: act_skbmod: Skip non-Ethernet packets 



[ Upstream commit 727d6a8b7ef3d25080fad228b2c4a1d4da5999c6 ]

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.

Fixes: 86da71b5 ("net_sched: Introduce skbmod action")
Reviewed-by: default avatarCong Wang <cong.wang@bytedance.com>
Signed-off-by: default avatarPeilin Ye <peilin.ye@bytedance.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent c278b954

net/sched/act_skbmod.c

+8 −4
Original line number Diff line number Diff line
@@ -6,6 +6,7 @@ 
*/



#include <linux/module.h>

#include <linux/if_arp.h>

#include <linux/init.h>

#include <linux/kernel.h>

#include <linux/skbuff.h>
@@ -33,6 +34,13 @@ static int tcf_skbmod_act(struct sk_buff *skb, const struct tc_action *a, 
	tcf_lastuse_update(&d->tcf_tm);

	bstats_cpu_update(this_cpu_ptr(d->common.cpu_bstats), skb);



	action = READ_ONCE(d->tcf_action);

	if (unlikely(action == TC_ACT_SHOT))

		goto drop;



	if (!skb->dev || skb->dev->type != ARPHRD_ETHER)

		return action;



	/* XXX: if you are going to edit more fields beyond ethernet header

	 * (example when you add IP header replacement or vlan swap)

	 * then MAX_EDIT_LEN needs to change appropriately
@@ -41,10 +49,6 @@ static int tcf_skbmod_act(struct sk_buff *skb, const struct tc_action *a, 
	if (unlikely(err)) /* best policy is to drop on the floor */

		goto drop;



	action = READ_ONCE(d->tcf_action);

	if (unlikely(action == TC_ACT_SHOT))

		goto drop;



	p = rcu_dereference_bh(d->skbmod_p);

	flags = p->flags;

	if (flags & SKBMOD_F_DMAC)