net: sched: act_csum: validate nested VLAN headers

tcf_csum_act() walks nested VLAN headers directly from skb->data when an
skb still carries in-payload VLAN tags. The current code reads
vlan->h_vlan_encapsulated_proto and then pulls VLAN_HLEN bytes without
first ensuring that the full VLAN header is present in the linear area.

If only part of an inner VLAN header is linearized, accessing
h_vlan_encapsulated_proto reads past the linear area, and the following
skb_pull(VLAN_HLEN) may violate skb invariants.

Fix this by requiring pskb_may_pull(skb, VLAN_HLEN) before accessing and
pulling each nested VLAN header. If the header still is not fully
available, drop the packet through the existing error path.

Fixes: 2ecba2d1e45b ("net: sched: act_csum: Fix csum calc for tagged packets")
Reported-by: Yifan Wu <yifanwucs@gmail.com>
Reported-by: Juefei Pu <tomapufckgml@gmail.com>
Co-developed-by: Yuan Tan <yuantan098@gmail.com>
Signed-off-by: Yuan Tan <yuantan098@gmail.com>
Suggested-by: Xin Liu <bird@lzu.edu.cn>
Tested-by: Ren Wei <enjou1224z@gmail.com>
Signed-off-by: Ruide Cao <caoruide123@gmail.com>
Signed-off-by: Ren Wei <n05ec@lzu.edu.cn>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/22df2fcb49f410203eafa5d97963dd36089f4ecf.1774892775.git.caoruide123@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/sched/act_csum.c b/net/sched/act_csum.c
index 213e1ce9d2da032fd878c663b722d8afd5429590..a9e4635d899e387884f21df981051cdaf2bad437 100644 (file)
--- a/net/sched/act_csum.c
+++ b/net/sched/act_csum.c
@@ -604,8 +604,12 @@ again:
                        protocol = skb->protocol;
                        orig_vlan_tag_present = true;
                } else {
-                       struct vlan_hdr *vlan = (struct vlan_hdr *)skb->data;
+                       struct vlan_hdr *vlan;
 
+                       if (!pskb_may_pull(skb, VLAN_HLEN))
+                               goto drop;
+
+                       vlan = (struct vlan_hdr *)skb->data;
                        protocol = vlan->h_vlan_encapsulated_proto;
                        skb_pull(skb, VLAN_HLEN);
                        skb_reset_network_header(skb);