netdev - Re: [PATCH net v2] net: ethernet: ti: am65-cpsw: fix freeing IRQ in am65_cpsw_nuss_remove_tx

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Message-ID: <2d6de2f0-09a7-4d1a-9288-6a9786256b12@intel.com>
Date: Fri, 17 Jan 2025 16:40:49 -0800
From: Jacob Keller <jacob.e.keller@...el.com>
To: Roger Quadros <rogerq@...nel.org>, Andrew Lunn <andrew+netdev@...n.ch>,
	"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, "Grygorii
 Strashko" <grygorii.strashko@...com>, Siddharth Vadapalli
	<s-vadapalli@...com>
CC: <srk@...com>, <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	Simon Horman <horms@...nel.org>
Subject: Re: [PATCH net v2] net: ethernet: ti: am65-cpsw: fix freeing IRQ in
 am65_cpsw_nuss_remove_tx_chns()



On 1/16/2025 5:54 AM, Roger Quadros wrote:
> When getting the IRQ we use k3_udma_glue_tx_get_irq() which returns
> negative error value on error. So not NULL check is not sufficient
> to deteremine if IRQ is valid. Check that IRQ is greater then zero
> to ensure it is valid.
> 

Using the phrase "NULL check" is a bit odd since the value returned
isn't a pointer. It is correct that checking for 0 is not sufficient
since it could be a negative error value. Given that IRQ numbers are
typically considered like an opaque object, perhaps thinking in terms of
pointers and NULL is common place. Either way, its not worth re-rolling
for a minor phrasing change like this.

Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>

> There is no issue at probe time but at runtime user can invoke
> .set_channels which results in the following call chain.
> am65_cpsw_set_channels()
>  am65_cpsw_nuss_update_tx_rx_chns()
>   am65_cpsw_nuss_remove_tx_chns()
>   am65_cpsw_nuss_init_tx_chns()
> 
> At this point if am65_cpsw_nuss_init_tx_chns() fails due to
> k3_udma_glue_tx_get_irq() then tx_chn->irq will be set to a
> negative value.
> 
> Then, at subsequent .set_channels with higher channel count we
> will attempt to free an invalid IRQ in am65_cpsw_nuss_remove_tx_chns()
> leading to a kernel warning.
> 
> The issue is present in the original commit that introduced this driver,
> although there, am65_cpsw_nuss_update_tx_rx_chns() existed as
> am65_cpsw_nuss_update_tx_chns().
> 
> Fixes: 93a76530316a ("net: ethernet: ti: introduce am65x/j721e gigabit eth subsystem driver")
> Signed-off-by: Roger Quadros <rogerq@...nel.org>
> Reviewed-by: Simon Horman <horms@...nel.org>
> Reviewed-by: Siddharth Vadapalli <s-vadapalli@...com>
> ---
> Changes in v2:
> - Fixed typo in commit log k3_udma_glue_rx_get_irq->k3_udma_glue_tx_get_irq
> - Added more details to commit log
> - Added Reviewed-by tags
> - Link to v1: https://lore.kernel.org/r/20250114-am65-cpsw-fix-tx-irq-free-v1-1-b2069e6ed185@kernel.org
> ---
>  drivers/net/ethernet/ti/am65-cpsw-nuss.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/ethernet/ti/am65-cpsw-nuss.c b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> index 5465bf872734..e1de45fb18ae 100644
> --- a/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> +++ b/drivers/net/ethernet/ti/am65-cpsw-nuss.c
> @@ -2248,7 +2248,7 @@ static void am65_cpsw_nuss_remove_tx_chns(struct am65_cpsw_common *common)
>  	for (i = 0; i < common->tx_ch_num; i++) {
>  		struct am65_cpsw_tx_chn *tx_chn = &common->tx_chns[i];
>  
> -		if (tx_chn->irq)
> +		if (tx_chn->irq > 0)
>  			devm_free_irq(dev, tx_chn->irq, tx_chn);
>  
>  		netif_napi_del(&tx_chn->napi_tx);
> 
> ---
> base-commit: 5bc55a333a2f7316b58edc7573e8e893f7acb532
> change-id: 20250114-am65-cpsw-fix-tx-irq-free-846ac55ee6e1
> 
> Best regards,