[PATCH net v3] vmxnet3: fix BUG_ON in vmxnet3_get_hdr_len() for Geneve packets

[Harshaka Narayana]

vmxnet3_get_hdr_len() assumes gdesc->rcd.v4/v6/tcp always describe the
outer header, but for a Geneve-encapsulated packet the device can set
them based on the inner header instead, signalled by the
VMXNET3_RCD_HDR_INNER_SHIFT bit in the completion descriptor. Since the
function never skips the outer encapsulation, this mismatch triggers:

- BUG_ON(hdr.ipv4->protocol != IPPROTO_TCP), because the outer
  protocol is UDP (Geneve), not TCP.
- BUG_ON(hdr.eth->h_proto != ...), when the tunnel's outer and inner
  IP versions differ (e.g. outer IPv6/inner IPv4 or vice versa).

Check VMXNET3_RCD_HDR_INNER_SHIFT up front and bail out, since the
function cannot locate the inner header it would need to parse. Also
convert the remaining BUG_ON()s in this function to return 0
defensively.

Fixes: 45dac1d6ea04 ("vmxnet3: Changes for vmxnet3 adapter version 2 (fwd)")
Signed-off-by: Harshaka Narayana <harshaka.narayana@xxxxxxxxxxxx>
Reviewed-by: Ronak Doshi <ronak.doshi@xxxxxxxxxxxx>
Reviewed-by: Sankararaman Jayaraman <sankararaman.jayaraman@xxxxxxxxxxxx>
---
v3:
  - Combined the two early return-0 checks into one condition
  - Replaced stacked Signed-off-by tags with Reviewed-by for Ronak
    Doshi and Sankararaman Jayaraman
v2: https://lore.kernel.org/netdev/20260709201654.4108084-1-harshaka.narayana@xxxxxxxxxxxx/
  - Check VMXNET3_RCD_HDR_INNER_SHIFT up front to catch the Geneve
    inner-header case directly, and convert the remaining
    BUG_ON(hdr.eth->h_proto != ...) checks to return 0
  - Reworded commit message to describe the root cause via
    VMXNET3_RCD_HDR_INNER_SHIFT
v1: https://lore.kernel.org/netdev/20260707165248.1859188-1-harshaka.narayana@xxxxxxxxxxxx/
---
 drivers/net/vmxnet3/vmxnet3_drv.c | 22 ++++++++++++++++------
 1 file changed, 16 insertions(+), 6 deletions(-)

diff --git a/drivers/net/vmxnet3/vmxnet3_drv.c b/drivers/net/vmxnet3/vmxnet3_drv.c
index 40522afc0532..f8df83f9965d 100644
--- a/drivers/net/vmxnet3/vmxnet3_drv.c
+++ b/drivers/net/vmxnet3/vmxnet3_drv.c
@@ -1530,7 +1530,11 @@ vmxnet3_get_hdr_len(struct vmxnet3_adapter *adapter, struct sk_buff *skb,
 		struct ipv6hdr *ipv6;
 		struct tcphdr *tcp;
 	} hdr;
-	BUG_ON(gdesc->rcd.tcp == 0);
+
+	/* v4/v6/tcp then describe the inner header, which we can't locate. */
+	if ((le32_to_cpu(gdesc->dword[0]) & (1UL << VMXNET3_RCD_HDR_INNER_SHIFT)) ||
+	    gdesc->rcd.tcp == 0)
+		return 0;
 
 	maplen = skb_headlen(skb);
 	if (unlikely(sizeof(struct iphdr) + sizeof(struct tcphdr) > maplen))
@@ -1544,15 +1548,21 @@ vmxnet3_get_hdr_len(struct vmxnet3_adapter *adapter, struct sk_buff *skb,
 
 	hdr.eth = eth_hdr(skb);
 	if (gdesc->rcd.v4) {
-		BUG_ON(hdr.eth->h_proto != htons(ETH_P_IP) &&
-		       hdr.veth->h_vlan_encapsulated_proto != htons(ETH_P_IP));
+		if (hdr.eth->h_proto != htons(ETH_P_IP) &&
+		    hdr.veth->h_vlan_encapsulated_proto != htons(ETH_P_IP))
+			return 0;
+
 		hdr.ptr += hlen;
-		BUG_ON(hdr.ipv4->protocol != IPPROTO_TCP);
+		if (hdr.ipv4->protocol != IPPROTO_TCP)
+			return 0;
+
 		hlen = hdr.ipv4->ihl << 2;
 		hdr.ptr += hdr.ipv4->ihl << 2;
 	} else if (gdesc->rcd.v6) {
-		BUG_ON(hdr.eth->h_proto != htons(ETH_P_IPV6) &&
-		       hdr.veth->h_vlan_encapsulated_proto != htons(ETH_P_IPV6));
+		if (hdr.eth->h_proto != htons(ETH_P_IPV6) &&
+		    hdr.veth->h_vlan_encapsulated_proto != htons(ETH_P_IPV6))
+			return 0;
+
 		hdr.ptr += hlen;
 		/* Use an estimated value, since we also need to handle
 		 * TSO case.
-- 
2.52.0