[PATCH net v2] net: sfc: fix using uninitialized xdp tx_queue

[PATCH net v2] net: sfc: fix using uninitialized xdp tx_queue

[Taehee Yoo]

In some cases, xdp tx_queue can get used before initialization.
1. interface up/down
2. ring buffer size change

When CPU cores are lower than maximum number of channels of sfc driver,
it creates new channels only for XDP.

When an interface is up or ring buffer size is changed, all channels
are initialized.
But xdp channels are always initialized later.
So, the below scenario is possible.
Packets are received to rx queue of normal channels and it is acted
XDP_TX and tx_queue of xdp channels get used.
But these tx_queues are not initialized yet.
If so, TX DMA or queue error occurs.

In order to avoid this problem.
1. initializes xdp tx_queues earlier than other rx_queue in
efx_start_channels().
2. checks whether tx_queue is initialized or not in efx_xdp_tx_buffers().

Splat looks like:
   sfc 0000:08:00.1 enp8s0f1np1: TX queue 10 spurious TX completion id 250
   sfc 0000:08:00.1 enp8s0f1np1: resetting (RECOVER_OR_ALL)
   sfc 0000:08:00.1 enp8s0f1np1: MC command 0x80 inlen 100 failed rc=-22
   (raw=22) arg=789
   sfc 0000:08:00.1 enp8s0f1np1: has been disabled

Fixes: f28100cb9c96 ("sfc: fix lack of XDP TX queues - error XDP TX failed (-22)")
Acked-by: Martin Habets <habetsm.xilinx@gmail.com>
Signed-off-by: Taehee Yoo <ap420073@gmail.com>
---

v2:
 - Change Fixes tag
 - Add Acked tag

 drivers/net/ethernet/sfc/efx_channels.c | 2 +-
 drivers/net/ethernet/sfc/tx.c           | 3 +++
 drivers/net/ethernet/sfc/tx_common.c    | 2 ++
 3 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/sfc/efx_channels.c b/drivers/net/ethernet/sfc/efx_channels.c
index 83e27231fbe6..377df8b7f015 100644
--- a/drivers/net/ethernet/sfc/efx_channels.c
+++ b/drivers/net/ethernet/sfc/efx_channels.c
@@ -1140,7 +1140,7 @@ void efx_start_channels(struct efx_nic *efx)
 	struct efx_rx_queue *rx_queue;
 	struct efx_channel *channel;
 
-	efx_for_each_channel(channel, efx) {
+	efx_for_each_channel_rev(channel, efx) {
 		efx_for_each_channel_tx_queue(tx_queue, channel) {
 			efx_init_tx_queue(tx_queue);
 			atomic_inc(&efx->active_queues);
diff --git a/drivers/net/ethernet/sfc/tx.c b/drivers/net/ethernet/sfc/tx.c
index d16e031e95f4..6983799e1c05 100644
--- a/drivers/net/ethernet/sfc/tx.c
+++ b/drivers/net/ethernet/sfc/tx.c
@@ -443,6 +443,9 @@ int efx_xdp_tx_buffers(struct efx_nic *efx, int n, struct xdp_frame **xdpfs,
 	if (unlikely(!tx_queue))
 		return -EINVAL;
 
+	if (!tx_queue->initialised)
+		return -EINVAL;
+
 	if (efx->xdp_txq_queues_mode != EFX_XDP_TX_QUEUES_DEDICATED)
 		HARD_TX_LOCK(efx->net_dev, tx_queue->core_txq, cpu);
 
diff --git a/drivers/net/ethernet/sfc/tx_common.c b/drivers/net/ethernet/sfc/tx_common.c
index d530cde2b864..9bc8281b7f5b 100644
--- a/drivers/net/ethernet/sfc/tx_common.c
+++ b/drivers/net/ethernet/sfc/tx_common.c
@@ -101,6 +101,8 @@ void efx_fini_tx_queue(struct efx_tx_queue *tx_queue)
 	netif_dbg(tx_queue->efx, drv, tx_queue->efx->net_dev,
 		  "shutting down TX queue %d\n", tx_queue->queue);
 
+	tx_queue->initialised = false;
+
 	if (!tx_queue->buffer)
 		return;
 
-- 
2.17.1

Re: [PATCH net v2] net: sfc: fix using uninitialized xdp tx_queue

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net.git (master)
by David S. Miller <davem@davemloft.net>:

On Tue,  5 Apr 2022 08:45:44 +0000 you wrote:
> In some cases, xdp tx_queue can get used before initialization.
> 1. interface up/down
> 2. ring buffer size change
> 
> When CPU cores are lower than maximum number of channels of sfc driver,
> it creates new channels only for XDP.
> 
> [...]

Here is the summary with links:
  - [net,v2] net: sfc: fix using uninitialized xdp tx_queue
    https://git.kernel.org/netdev/net/c/fb5833d81e43

You are awesome, thank you!
-- 
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