netdev - RE: [PATCH net 1/8] net: enetc: fix the off-by-one issue in enetc_map_tx

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Message-ID:
 <AS8PR04MB8849FB282339EB6D5DC2637396FB2@AS8PR04MB8849.eurprd04.prod.outlook.com>
Date: Mon, 17 Feb 2025 20:56:29 +0000
From: Claudiu Manoil <claudiu.manoil@....com>
To: Wei Fang <wei.fang@....com>, Vladimir Oltean <vladimir.oltean@....com>,
	Clark Wang <xiaoning.wang@....com>, "andrew+netdev@...n.ch"
	<andrew+netdev@...n.ch>, "davem@...emloft.net" <davem@...emloft.net>,
	"edumazet@...gle.com" <edumazet@...gle.com>, "kuba@...nel.org"
	<kuba@...nel.org>, "pabeni@...hat.com" <pabeni@...hat.com>
CC: Ioana Ciornei <ioana.ciornei@....com>, "Y.B. Lu" <yangbo.lu@....com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"imx@...ts.linux.dev" <imx@...ts.linux.dev>, "stable@...r.kernel.org"
	<stable@...r.kernel.org>
Subject: RE: [PATCH net 1/8] net: enetc: fix the off-by-one issue in
 enetc_map_tx_buffs()

> -----Original Message-----
> From: Wei Fang <wei.fang@....com>
> Sent: Monday, February 17, 2025 11:39 AM
[...]
> Subject: [PATCH net 1/8] net: enetc: fix the off-by-one issue in
> enetc_map_tx_buffs()
> 
> When the DMA mapping error occurs, it will attempt to free 'count + 1'

Hi Wei,
Are you sure?

dma_err occurs before count is incremented, at least that's the design.

First step already contradicts your claim:
```
static int enetc_map_tx_buffs(struct enetc_bdr *tx_ring, struct sk_buff *skb)
{
[...]
	int i, count = 0;
[...]
	dma = dma_map_single(tx_ring->dev, skb->data, len, DMA_TO_DEVICE);
	if (unlikely(dma_mapping_error(tx_ring->dev, dma)))
		goto dma_err;

===> count is 0 on goto path!
[...]
	count++;
```

Regards,
Claudiu