[PATCH] net: airoha: Fix off-by-one error in HTB rate-limit channel removal

[PATCH] net: airoha: Fix off-by-one error in HTB rate-limit channel removal

[Wayen Yan]

In airoha_tc_remove_htb_queue(), the rate-limit was being cleared
using (queue + 1) instead of queue, causing:
- The original channel rate-limit configuration to remain active
- The next channel to be incorrectly disabled
- Potential out-of-bounds access when queue == 3 (channel 4)

The alloc path (airoha_tc_htb_alloc_leaf_queue) correctly uses
channel (0..3), but the remove path incorrectly added 1.

Fix by using queue directly to match the alloc and rollback paths.

Fixes: ef1ca9271313 ("net: airoha: Add sched HTB offload support")
Signed-off-by: Wayen Yan <win847@gmail.com>
---
 drivers/net/ethernet/airoha/airoha_eth.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
index 31cdb11cd7..02807b3967 100644
--- a/drivers/net/ethernet/airoha/airoha_eth.c
+++ b/drivers/net/ethernet/airoha/airoha_eth.c
@@ -2805,7 +2805,7 @@ static void airoha_tc_remove_htb_queue(struct net_device *dev, int queue)
 	struct airoha_gdm_port *port = netdev_priv(dev);
 
 	netif_set_real_num_tx_queues(dev, dev->real_num_tx_queues - 1);
-	airoha_qdma_set_tx_rate_limit(dev, queue + 1, 0, 0);
+	airoha_qdma_set_tx_rate_limit(dev, queue, 0, 0);
 	clear_bit(queue, port->qos_sq_bmap);
 }
 
-- 
2.51.0

Re: [PATCH] net: airoha: Fix off-by-one error in HTB rate-limit channel removal

[Lorenzo Bianconi]

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> In airoha_tc_remove_htb_queue(), the rate-limit was being cleared
> using (queue + 1) instead of queue, causing:
> - The original channel rate-limit configuration to remain active
> - The next channel to be incorrectly disabled
> - Potential out-of-bounds access when queue == 3 (channel 4)
> 
> The alloc path (airoha_tc_htb_alloc_leaf_queue) correctly uses
> channel (0..3), but the remove path incorrectly added 1.
> 
> Fix by using queue directly to match the alloc and rollback paths.
> 
> Fixes: ef1ca9271313 ("net: airoha: Add sched HTB offload support")
> Signed-off-by: Wayen Yan <win847@gmail.com>
> ---
>  drivers/net/ethernet/airoha/airoha_eth.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/airoha/airoha_eth.c b/drivers/net/ethernet/airoha/airoha_eth.c
> index 31cdb11cd7..02807b3967 100644
> --- a/drivers/net/ethernet/airoha/airoha_eth.c
> +++ b/drivers/net/ethernet/airoha/airoha_eth.c
> @@ -2805,7 +2805,7 @@ static void airoha_tc_remove_htb_queue(struct net_device *dev, int queue)
>  	struct airoha_gdm_port *port = netdev_priv(dev);
>  
>  	netif_set_real_num_tx_queues(dev, dev->real_num_tx_queues - 1);
> -	airoha_qdma_set_tx_rate_limit(dev, queue + 1, 0, 0);
> +	airoha_qdma_set_tx_rate_limit(dev, queue, 0, 0);
>  	clear_bit(queue, port->qos_sq_bmap);
>  }

Please hold on with this patch, I am aware of the bug and the fix is already in
my queue [0]. I am just waiting the net-next to be merged into net in order to
avoid merge conflicts.

Regards,
Lorenzo

[0] https://github.com/LorenzoBianconi/net-next/commits/airoha-qos-fixes-for-net/

>  
> -- 
> 2.51.0
> 
> 

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