Commit fa4e0f88 authored by Davide Caratti's avatar Davide Caratti Committed by David S. Miller
Browse files

net/sched: fix corrupted L2 header with MPLS 'push' and 'pop' actions 



the following script:

 # tc qdisc add dev eth0 clsact
 # tc filter add dev eth0 egress protocol ip matchall \
 > action mpls push protocol mpls_uc label 0x355aa bos 1

causes corruption of all IP packets transmitted by eth0. On TC egress, we
can't rely on the value of skb->mac_len, because it's 0 and a MPLS 'push'
operation will result in an overwrite of the first 4 octets in the packet
L2 header (e.g. the Destination Address if eth0 is an Ethernet); the same
error pattern is present also in the MPLS 'pop' operation. Fix this error
in act_mpls data plane, computing 'mac_len' as the difference between the
network header and the mac header (when not at TC ingress), and use it in
MPLS 'push'/'pop' core functions.

v2: unbreak 'make htmldocs' because of missing documentation of 'mac_len'
    in skb_mpls_pop(), reported by kbuild test robot

CC: Lorenzo Bianconi <lorenzo@kernel.org>
Fixes: 2a2ea508 ("net: sched: add mpls manipulation actions to TC")
Reviewed-by: default avatarSimon Horman <simon.horman@netronome.com>
Acked-by: default avatarJohn Hurley <john.hurley@netronome.com>
Signed-off-by: default avatarDavide Caratti <dcaratti@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent dedc5a08

include/linux/skbuff.h

+3 −2
Original line number Diff line number Diff line
@@ -3510,8 +3510,9 @@ int skb_ensure_writable(struct sk_buff *skb, int write_len); 
int __skb_vlan_pop(struct sk_buff *skb, u16 *vlan_tci);

int skb_vlan_pop(struct sk_buff *skb);

int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci);

int skb_mpls_push(struct sk_buff *skb, __be32 mpls_lse, __be16 mpls_proto);

int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto);

int skb_mpls_push(struct sk_buff *skb, __be32 mpls_lse, __be16 mpls_proto,

		  int mac_len);

int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto, int mac_len);

int skb_mpls_update_lse(struct sk_buff *skb, __be32 mpls_lse);

int skb_mpls_dec_ttl(struct sk_buff *skb);

struct sk_buff *pskb_extract(struct sk_buff *skb, int off, int to_copy,

net/core/skbuff.c

+11 −8
Original line number Diff line number Diff line
@@ -5477,12 +5477,14 @@ static void skb_mod_eth_type(struct sk_buff *skb, struct ethhdr *hdr, 
 * @skb: buffer

 * @mpls_lse: MPLS label stack entry to push

 * @mpls_proto: ethertype of the new MPLS header (expects 0x8847 or 0x8848)

 * @mac_len: length of the MAC header

 *

 * Expects skb->data at mac header.

 *

 * Returns 0 on success, -errno otherwise.

 */

int skb_mpls_push(struct sk_buff *skb, __be32 mpls_lse, __be16 mpls_proto)

int skb_mpls_push(struct sk_buff *skb, __be32 mpls_lse, __be16 mpls_proto,

		  int mac_len)

{

	struct mpls_shim_hdr *lse;

	int err;
@@ -5499,15 +5501,15 @@ int skb_mpls_push(struct sk_buff *skb, __be32 mpls_lse, __be16 mpls_proto) 
		return err;



	if (!skb->inner_protocol) {

		skb_set_inner_network_header(skb, skb->mac_len);

		skb_set_inner_network_header(skb, mac_len);

		skb_set_inner_protocol(skb, skb->protocol);

	}



	skb_push(skb, MPLS_HLEN);

	memmove(skb_mac_header(skb) - MPLS_HLEN, skb_mac_header(skb),

		skb->mac_len);

		mac_len);

	skb_reset_mac_header(skb);

	skb_set_network_header(skb, skb->mac_len);

	skb_set_network_header(skb, mac_len);



	lse = mpls_hdr(skb);

	lse->label_stack_entry = mpls_lse;
@@ -5526,29 +5528,30 @@ EXPORT_SYMBOL_GPL(skb_mpls_push); 
 *

 * @skb: buffer

 * @next_proto: ethertype of header after popped MPLS header

 * @mac_len: length of the MAC header

 *

 * Expects skb->data at mac header.

 *

 * Returns 0 on success, -errno otherwise.

 */

int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto)

int skb_mpls_pop(struct sk_buff *skb, __be16 next_proto, int mac_len)

{

	int err;



	if (unlikely(!eth_p_mpls(skb->protocol)))

		return 0;



	err = skb_ensure_writable(skb, skb->mac_len + MPLS_HLEN);

	err = skb_ensure_writable(skb, mac_len + MPLS_HLEN);

	if (unlikely(err))

		return err;



	skb_postpull_rcsum(skb, mpls_hdr(skb), MPLS_HLEN);

	memmove(skb_mac_header(skb) + MPLS_HLEN, skb_mac_header(skb),

		skb->mac_len);

		mac_len);



	__skb_pull(skb, MPLS_HLEN);

	skb_reset_mac_header(skb);

	skb_set_network_header(skb, skb->mac_len);

	skb_set_network_header(skb, mac_len);



	if (skb->dev && skb->dev->type == ARPHRD_ETHER) {

		struct ethhdr *hdr;

net/openvswitch/actions.c

+3 −2
Original line number Diff line number Diff line
@@ -165,7 +165,8 @@ static int push_mpls(struct sk_buff *skb, struct sw_flow_key *key, 
{

	int err;



	err = skb_mpls_push(skb, mpls->mpls_lse, mpls->mpls_ethertype);

	err = skb_mpls_push(skb, mpls->mpls_lse, mpls->mpls_ethertype,

			    skb->mac_len);

	if (err)

		return err;
@@ -178,7 +179,7 @@ static int pop_mpls(struct sk_buff *skb, struct sw_flow_key *key, 
{

	int err;



	err = skb_mpls_pop(skb, ethertype);

	err = skb_mpls_pop(skb, ethertype, skb->mac_len);

	if (err)

		return err;

net/sched/act_mpls.c

+8 −4
Original line number Diff line number Diff line
@@ -55,7 +55,7 @@ static int tcf_mpls_act(struct sk_buff *skb, const struct tc_action *a, 
	struct tcf_mpls *m = to_mpls(a);

	struct tcf_mpls_params *p;

	__be32 new_lse;

	int ret;

	int ret, mac_len;



	tcf_lastuse_update(&m->tcf_tm);

	bstats_cpu_update(this_cpu_ptr(m->common.cpu_bstats), skb);
@@ -63,8 +63,12 @@ static int tcf_mpls_act(struct sk_buff *skb, const struct tc_action *a, 
	/* Ensure 'data' points at mac_header prior calling mpls manipulating

	 * functions.

	 */

	if (skb_at_tc_ingress(skb))

	if (skb_at_tc_ingress(skb)) {

		skb_push_rcsum(skb, skb->mac_len);

		mac_len = skb->mac_len;

	} else {

		mac_len = skb_network_header(skb) - skb_mac_header(skb);

	}



	ret = READ_ONCE(m->tcf_action);
@@ -72,12 +76,12 @@ static int tcf_mpls_act(struct sk_buff *skb, const struct tc_action *a, 


	switch (p->tcfm_action) {

	case TCA_MPLS_ACT_POP:

		if (skb_mpls_pop(skb, p->tcfm_proto))

		if (skb_mpls_pop(skb, p->tcfm_proto, mac_len))

			goto drop;

		break;

	case TCA_MPLS_ACT_PUSH:

		new_lse = tcf_mpls_get_lse(NULL, p, !eth_p_mpls(skb->protocol));

		if (skb_mpls_push(skb, new_lse, p->tcfm_proto))

		if (skb_mpls_push(skb, new_lse, p->tcfm_proto, mac_len))

			goto drop;

		break;

	case TCA_MPLS_ACT_MODIFY:

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