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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: 2a2ea50870 ("net: sched: add mpls manipulation actions to TC")
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Acked-by: John Hurley <john.hurley@netronome.com>
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Davide Caratti 2019-10-12 13:55:07 +02:00 committed by David S. Miller
parent dedc5a08da
commit fa4e0f8855
4 changed files with 25 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/skbuff.h
View File

@ -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,

19
net/core/skbuff.c
View File

@ -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;

5
net/openvswitch/actions.c
View File

@ -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;

12
net/sched/act_mpls.c
View File

@ -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: