[Intel-wired-lan] [net,v1] ice: Fix l2-fwd-offload toggle crash

[Benjamin Mikailenko]

Running netperf traffic and toggling l2-fwd-offload in quick succession
caused the driver to crash.

BUG: kernel NULL pointer dereference, address: 0000000000000020
[  861.517803] #PF: supervisor read access in kernel mode
[  861.517805] #PF: error_code(0x0000) - not-present page
[  861.517808] PGD 0 P4D 0
[  861.517811] Oops: 0000 [#1] PREEMPT SMP PTI
[  861.517815] CPU: 60 PID: 16471 Comm: netperf Kdump: loaded Tainted: G S
[  861.517818] Hardware name: Intel Corporation S2600WTT/S2600WTT, BIOS SE
[  861.517820] RIP: 0010:ice_start_xmit+0xb0/0x1420 [ice]

This crash would happen because during l2-fwd-offload configuration,
ice_init_macvlan or ice_deinit_macvlan would temporarily work on Tx rings.
At the same time, ice_start_xmit would attempt to select the correct send
buffer from Tx rings but reach a NULL pointer.

Fix this by checking if ring exists before proceeding xmit. If ring does
not exist, return NETDEV_TX_BUSY.

Fixes: 2b245cb29421 ("ice: Implement transmit and NAPI support")
Signed-off-by: Benjamin Mikailenko <benjamin.mikailenko at intel.com>
---
 drivers/net/ethernet/intel/ice/ice_txrx.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c b/drivers/net/ethernet/intel/ice/ice_txrx.c
index 086f0b3ab68d..96bc8fad39c0 100644
--- a/drivers/net/ethernet/intel/ice/ice_txrx.c
+++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
@@ -2405,6 +2405,8 @@ netdev_tx_t ice_start_xmit(struct sk_buff *skb, struct net_device *netdev)
 	struct ice_tx_ring *tx_ring;
 
 	tx_ring = vsi->tx_rings[skb->queue_mapping];
+	if (!tx_ring)
+		return NETDEV_TX_BUSY;
 
 	/* hardware can't handle really short frames, hardware padding works
 	 * beyond this point
-- 
2.34.3