[PATCH linux next v2] net: stmmac: remove software VLAN tag stripping

Problem
=======
When the stmmac driver has NETIF_F_HW_VLAN_STAG_RX enabled by default,
but the hardware does not support hardware stripping of ETH_P_8021AD
(VLAN 802.1ad) tags, the driver falls back to software stripping in
stmmac_rx_vlan(). If the received VLAN packet is fragmented and the
VLAN header resides in the non-linear part of the skb, the driver
attempts to pull the header without first ensuring it is linearized.
This leads to a kernel BUG in __skb_pull() due to invalid header
access.

Crash log
=========
[   72.212903] kernel BUG at include/linux/skbuff.h:2700!
[   72.212908] Kernel BUG [#1]
..
[   72.212958] [<ffffffff846919d2>] eth_type_trans+0xe2/0x168
[   72.212962] [<ffffffff844672e2>] stmmac_rx+0x602/0xc58
[   72.212966] [<ffffffff84467984>] stmmac_napi_poll_rx+0x4c/0xb8
[   72.212970] [<ffffffff84635246>] __napi_poll+0x2e/0x1e0
[   72.212975] [<ffffffff8463596e>] net_rx_action+0x31e/0x388
[   72.212979] [<ffffffff83c329b0>] handle_softirqs+0x170/0x358
[   72.212983] [<ffffffff83c32cc6>] __irq_exit_rcu+0xd6/0x100
[   72.212986] [<ffffffff83c32ee0>] irq_exit_rcu+0x18/0x28
[   72.212989] [<ffffffff84895b1e>] handle_riscv_irq+0x66/0x78
[   72.212994] [<ffffffff84896728>] do_irq+0x60/0xa0

Root cause
==========
In the software VLAN stripping path, stmmac_rx_vlan() does not call
pskb_may_pull() to ensure that the Ethernet header plus VLAN header
are in the linear area. As a result, __skb_pull() operates on an
skb with insufficient linear data, triggering the BUG check.

Solution
========
The software VLAN stripping logic in stmmac_rx_vlan() was originally
introduced in 2014 by commit b93819854d6e ("stmmac: Add vlan rx for
better GRO performance.") as a workaround to improve GRO performance,
since at that time GRO could not handle frames with VLAN tags. However,
this limitation was resolved in 2015 by commit 66e5133f19e9 ("vlan: Add
GRO support for non hardware accelerated vlan"), which added GRO support
for non-hardware-accelerated VLAN frames. Keeping a software fallback
path for VLAN stripping is no longer necessary and only adds complexity.

Rather than fixing the issue by adding pskb_may_pull() checks to
stmmac_rx_vlan(), remove the function entirely. Additionally, ensure
that hardware VLAN stripping features are only reported via
dev->hw_features when the hardware truly supports them.

Fixes: b93819854d6e ("stmmac: Add vlan rx for better GRO performance.")
Signed-off-by: Peilin He <redacted>
Reviewed-by: xu xin <xu.xin16@zte.com.cn>
Reviewed-by: Jiang Kun <redacted>
---
 .../net/ethernet/stmicro/stmmac/stmmac_main.c | 27 ++-----------------
 1 file changed, 2 insertions(+), 25 deletions(-)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index b2b7d0242dd3..790b7362048e 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -5021,24 +5021,6 @@ static netdev_features_t stmmac_features_check(struct sk_buff *skb,
 	return vlan_features_check(skb, features);
 }

-static void stmmac_rx_vlan(struct net_device *dev, struct sk_buff *skb)
-{
-	struct vlan_ethhdr *veth = skb_vlan_eth_hdr(skb);
-	__be16 vlan_proto = veth->h_vlan_proto;
-	u16 vlanid;
-
-	if ((vlan_proto == htons(ETH_P_8021Q) &&
-	     dev->features & NETIF_F_HW_VLAN_CTAG_RX) ||
-	    (vlan_proto == htons(ETH_P_8021AD) &&
-	     dev->features & NETIF_F_HW_VLAN_STAG_RX)) {
-		/* pop the vlan tag */
-		vlanid = ntohs(veth->h_vlan_TCI);
-		memmove(skb->data + VLAN_HLEN, veth, ETH_ALEN * 2);
-		skb_pull(skb, VLAN_HLEN);
-		__vlan_hwaccel_put_tag(skb, vlan_proto, vlanid);
-	}
-}
-
 /**
  * stmmac_rx_refill - refill used skb preallocated buffers
  * @priv: driver private structure

@@ -5407,9 +5389,7 @@ static void stmmac_dispatch_skb_zc(struct stmmac_priv *priv, u32 queue,
 	if (priv->hw->hw_vlan_en)
 		/* MAC level stripping. */
 		stmmac_rx_hw_vlan(priv, priv->hw, p, skb);
-	else
-		/* Driver level stripping. */
-		stmmac_rx_vlan(priv->dev, skb);
+
 	skb->protocol = eth_type_trans(skb, priv->dev);

 	if (unlikely(!coe) || !stmmac_has_ip_ethertype(skb))

@@ -5901,9 +5881,6 @@ static int stmmac_rx(struct stmmac_priv *priv, int limit, u32 queue)
 		if (priv->hw->hw_vlan_en)
 			/* MAC level stripping. */
 			stmmac_rx_hw_vlan(priv, priv->hw, p, skb);
-		else
-			/* Driver level stripping. */
-			stmmac_rx_vlan(priv->dev, skb);

 		skb->protocol = eth_type_trans(skb, priv->dev);

@@ -7965,7 +7942,7 @@ static int __stmmac_dvr_probe(struct device *device,
 	ndev->watchdog_timeo = msecs_to_jiffies(watchdog);
 #ifdef STMMAC_VLAN_TAG_USED
 	/* Both mac100 and gmac support receive VLAN tag detection */
-	ndev->features |= NETIF_F_HW_VLAN_CTAG_RX | NETIF_F_HW_VLAN_STAG_RX;
+	ndev->features |= NETIF_F_HW_VLAN_CTAG_RX;
 	if (dwmac_is_xmac(priv->plat->core_type)) {
 		ndev->hw_features |= NETIF_F_HW_VLAN_CTAG_RX;
 		priv->hw->hw_vlan_en = true;

-- 
2.27.0