[PATCH 6.18 249/396] vxlan: use pskb_network_may_pull() in route_shortcircuit()

6.18-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <[email protected]>

commit 26bb2dd0a8839617e2c79ffbbe1923f8e4bab9fb upstream.

route_shortcircuit() currently calls pskb_may_pull(skb, sizeof(struct iphdr))
(or ipv6hdr), which checks if bytes are available starting from skb->data.

However, in vxlan_xmit(), skb->data points to the MAC header, so
skb_network_offset(skb) is ETH_HLEN (14 bytes). Using pskb_may_pull(skb, 20)
only checks 20 bytes from skb->data (which is 14 bytes MAC header + 6 bytes of
IP header), leaving the rest of the IP header potentially un-pulled in non-linear
frags. Subsequent dereferences of ip_hdr(skb)->daddr can read beyond the pulled
linear buffer length.

Fix this by using pskb_network_may_pull(), which adds skb_network_offset(skb) to
the length check to ensure the full network header is present in the linear buffer.

Fixes: e4f67addf158 ("add DOVE extensions for VXLAN")
Cc: [email protected]
Signed-off-by: Eric Dumazet <[email protected]>
Reviewed-by: Vadim Fedorenko <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
 drivers/net/vxlan/vxlan_core.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/net/vxlan/vxlan_core.c
+++ b/drivers/net/vxlan/vxlan_core.c
@@ -2115,7 +2115,7 @@ static bool route_shortcircuit(struct ne
 	{
 		struct iphdr *pip;
 
-		if (!pskb_may_pull(skb, sizeof(struct iphdr)))
+		if (!pskb_network_may_pull(skb, sizeof(struct iphdr)))
 			return false;
 		pip = ip_hdr(skb);
 		n = neigh_lookup(&arp_tbl, &pip->daddr, dev);
@@ -2141,7 +2141,7 @@ static bool route_shortcircuit(struct ne
 		 */
 		if (!ipv6_stub->nd_tbl)
 			return false;
-		if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
+		if (!pskb_network_may_pull(skb, sizeof(struct ipv6hdr)))
 			return false;
 		pip6 = ipv6_hdr(skb);
 		n = neigh_lookup(ipv6_stub->nd_tbl, &pip6->daddr, dev);