linux-kernel - RE: [PATCH v2 net 9/9] net: enetc: fix the off-by-one issue in enetc_map_tx_tso

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Message-ID:
 <PAXPR04MB85106BF748386C843FE28C6488C42@PAXPR04MB8510.eurprd04.prod.outlook.com>
Date: Thu, 20 Feb 2025 05:06:46 +0000
From: Wei Fang <wei.fang@....com>
To: Claudiu Manoil <claudiu.manoil@....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>,
	"michal.swiatkowski@...ux.intel.com" <michal.swiatkowski@...ux.intel.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 v2 net 9/9] net: enetc: fix the off-by-one issue in
 enetc_map_tx_tso_buffs()

> > -----Original Message-----
> > From: Wei Fang <wei.fang@....com>
> > Sent: Wednesday, February 19, 2025 7:43 AM
> [...]
> > Subject: [PATCH v2 net 9/9] net: enetc: fix the off-by-one issue in
> > enetc_map_tx_tso_buffs()
> >
> > There is an off-by-one issue for the err_chained_bd path, it will free
> > one more tx_swbd than expected. But there is no such issue for the
> > err_map_data path. To fix this off-by-one issue and make the two error
> > handling consistent, the loop condition of error handling is modified
> > and the 'count++' operation is moved before enetc_map_tx_tso_data().
> >
> > Fixes: fb8629e2cbfc ("net: enetc: add support for software TSO")
> > Cc: stable@...r.kernel.org
> > Signed-off-by: Wei Fang <wei.fang@....com>
> > ---
> >  drivers/net/ethernet/freescale/enetc/enetc.c | 6 +++---
> >  1 file changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c
> > b/drivers/net/ethernet/freescale/enetc/enetc.c
> > index 9a24d1176479..fe3967268a19 100644
> > --- a/drivers/net/ethernet/freescale/enetc/enetc.c
> > +++ b/drivers/net/ethernet/freescale/enetc/enetc.c
> > @@ -832,6 +832,7 @@ static int enetc_map_tx_tso_buffs(struct enetc_bdr
> > *tx_ring, struct sk_buff *skb
> >  			txbd = ENETC_TXBD(*tx_ring, i);
> >  			tx_swbd = &tx_ring->tx_swbd[i];
> >  			prefetchw(txbd);
> > +			count++;
> >
> >  			/* Compute the checksum over this segment of data and
> >  			 * add it to the csum already computed (over the L4
> > @@ -848,7 +849,6 @@ static int enetc_map_tx_tso_buffs(struct enetc_bdr
> > *tx_ring, struct sk_buff *skb
> >  				goto err_map_data;
> >
> >  			data_len -= size;
> > -			count++;
> 
> Hi Wei,
> 
> My issue is that:
> enetc_map_tx_tso_hdr() not only updates the current tx_swbd (so 1 count++
> needed), but in case of extension flag it advances 'tx_swbd' and 'i' with
> another
> position so and extra 'count++' would be needed in that case.
> 

I think the patch 2 (net: enetc: correct the tx_swbd statistics) is to resolve
your issue.