6.1-stable review patch. If anyone has any objections, please let me know.
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From: Vladimir Oltean vladimir.oltean@nxp.com
[ Upstream commit 0bcf2e4aca6c29a07555b713f2fb461dc38d5977 ]
ocelot_xmit_get_vlan_info() calls __skb_vlan_pop() as the most appropriate helper I could find which strips away a VLAN header. That's all I need it to do, but __skb_vlan_pop() has more logic, which will become incompatible with the future revert of commit 6d1ccff62780 ("net: reset mac header in dev_start_xmit()").
Namely, it performs a sanity check on skb_mac_header(), which will stop being set after the above revert, so it will return an error instead of removing the VLAN tag.
ocelot_xmit_get_vlan_info() gets called in 2 circumstances:
(1) the port is under a VLAN-aware bridge and the bridge sends VLAN-tagged packets
(2) the port is under a VLAN-aware bridge and somebody else (an 8021q upper) sends VLAN-tagged packets (using a VID that isn't in the bridge vlan tables)
In case (1), there is actually no bug to defend against, because br_dev_xmit() calls skb_reset_mac_header() and things continue to work.
However, in case (2), illustrated using the commands below, it can be seen that our intervention is needed, since __skb_vlan_pop() complains:
$ ip link add br0 type bridge vlan_filtering 1 && ip link set br0 up $ ip link set $eth master br0 && ip link set $eth up $ ip link add link $eth name $eth.100 type vlan id 100 && ip link set $eth.100 up $ ip addr add 192.168.100.1/24 dev $eth.100
I could fend off the checks in __skb_vlan_pop() with some skb_mac_header_was_set() calls, but seeing how few callers of __skb_vlan_pop() there are from TX paths, that seems rather unproductive.
As an alternative solution, extract the bare minimum logic to strip a VLAN header, and move it to a new helper named vlan_remove_tag(), close to the definition of vlan_insert_tag(). Document it appropriately and make ocelot_xmit_get_vlan_info() call this smaller helper instead.
Seeing that it doesn't appear illegal to test skb->protocol in the TX path, I guess it would be a good for vlan_remove_tag() to also absorb the vlan_set_encap_proto() function call.
Signed-off-by: Vladimir Oltean vladimir.oltean@nxp.com Reviewed-by: Simon Horman simon.horman@corigine.com Reviewed-by: Florian Fainelli f.fainelli@gmail.com Reviewed-by: Eric Dumazet edumazet@google.com Signed-off-by: David S. Miller davem@davemloft.net Stable-dep-of: 67c3ca2c5cfe ("net: mscc: ocelot: use ocelot_xmit_get_vlan_info() also for FDMA and register injection") Signed-off-by: Sasha Levin sashal@kernel.org --- include/linux/if_vlan.h | 21 +++++++++++++++++++++ net/core/skbuff.c | 8 +------- net/dsa/tag_ocelot.c | 2 +- 3 files changed, 23 insertions(+), 8 deletions(-)
diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h index e0d0a645be7cf..83266201746c1 100644 --- a/include/linux/if_vlan.h +++ b/include/linux/if_vlan.h @@ -704,6 +704,27 @@ static inline void vlan_set_encap_proto(struct sk_buff *skb, skb->protocol = htons(ETH_P_802_2); }
+/** + * vlan_remove_tag - remove outer VLAN tag from payload + * @skb: skbuff to remove tag from + * @vlan_tci: buffer to store value + * + * Expects the skb to contain a VLAN tag in the payload, and to have skb->data + * pointing at the MAC header. + * + * Returns a new pointer to skb->data, or NULL on failure to pull. + */ +static inline void *vlan_remove_tag(struct sk_buff *skb, u16 *vlan_tci) +{ + struct vlan_hdr *vhdr = (struct vlan_hdr *)(skb->data + ETH_HLEN); + + *vlan_tci = ntohs(vhdr->h_vlan_TCI); + + memmove(skb->data + VLAN_HLEN, skb->data, 2 * ETH_ALEN); + vlan_set_encap_proto(skb, vhdr); + return __skb_pull(skb, VLAN_HLEN); +} + /** * skb_vlan_tagged - check if skb is vlan tagged. * @skb: skbuff to query diff --git a/net/core/skbuff.c b/net/core/skbuff.c index 4d46788cd493a..768b8d65a5baa 100644 --- a/net/core/skbuff.c +++ b/net/core/skbuff.c @@ -5791,7 +5791,6 @@ EXPORT_SYMBOL(skb_ensure_writable); */ int __skb_vlan_pop(struct sk_buff *skb, u16 *vlan_tci) { - struct vlan_hdr *vhdr; int offset = skb->data - skb_mac_header(skb); int err;
@@ -5807,13 +5806,8 @@ int __skb_vlan_pop(struct sk_buff *skb, u16 *vlan_tci)
skb_postpull_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
- vhdr = (struct vlan_hdr *)(skb->data + ETH_HLEN); - *vlan_tci = ntohs(vhdr->h_vlan_TCI); - - memmove(skb->data + VLAN_HLEN, skb->data, 2 * ETH_ALEN); - __skb_pull(skb, VLAN_HLEN); + vlan_remove_tag(skb, vlan_tci);
- vlan_set_encap_proto(skb, vhdr); skb->mac_header += VLAN_HLEN;
if (skb_network_offset(skb) < ETH_HLEN) diff --git a/net/dsa/tag_ocelot.c b/net/dsa/tag_ocelot.c index afca3cdf190a0..18dda9423fae5 100644 --- a/net/dsa/tag_ocelot.c +++ b/net/dsa/tag_ocelot.c @@ -26,7 +26,7 @@ static void ocelot_xmit_get_vlan_info(struct sk_buff *skb, struct dsa_port *dp, br_vlan_get_proto(br, &proto);
if (ntohs(hdr->h_vlan_proto) == proto) { - __skb_vlan_pop(skb, &tci); + vlan_remove_tag(skb, &tci); *vlan_tci = tci; } else { rcu_read_lock();