> -----Original Message-----
> From: Michal Swiatkowski <michal.swiatkowski@xxxxxxxxxxxxxxx>
> Sent: 2025年2月18日 13:45
> To: Wei Fang <wei.fang@xxxxxxx>
> Cc: Michal Swiatkowski <michal.swiatkowski@xxxxxxxxxxxxxxx>; Claudiu Manoil
> <claudiu.manoil@xxxxxxx>; Vladimir Oltean <vladimir.oltean@xxxxxxx>;
> Clark Wang <xiaoning.wang@xxxxxxx>; andrew+netdev@xxxxxxx;
> davem@xxxxxxxxxxxxx; edumazet@xxxxxxxxxx; kuba@xxxxxxxxxx;
> pabeni@xxxxxxxxxx; Ioana Ciornei <ioana.ciornei@xxxxxxx>; Y.B. Lu
> <yangbo.lu@xxxxxxx>; netdev@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> imx@xxxxxxxxxxxxxxx; stable@xxxxxxxxxxxxxxx
> Subject: Re: [PATCH net 1/8] net: enetc: fix the off-by-one issue in
> enetc_map_tx_buffs()
>
> On Tue, Feb 18, 2025 at 02:11:12AM +0000, Wei Fang wrote:
> > > > Fixes: d4fd0404c1c9 ("enetc: Introduce basic PF and VF ENETC ethernet
> > > drivers")
> > > > Cc: stable@xxxxxxxxxxxxxxx
> > > > Signed-off-by: Wei Fang <wei.fang@xxxxxxx>
> > > > ---
> > > > drivers/net/ethernet/freescale/enetc/enetc.c | 4 ++--
> > > > 1 file changed, 2 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/drivers/net/ethernet/freescale/enetc/enetc.c
> > > b/drivers/net/ethernet/freescale/enetc/enetc.c
> > > > index 6a6fc819dfde..f7bc2fc33a76 100644
> > > > --- a/drivers/net/ethernet/freescale/enetc/enetc.c
> > > > +++ b/drivers/net/ethernet/freescale/enetc/enetc.c
> > > > @@ -372,13 +372,13 @@ static int enetc_map_tx_buffs(struct
> enetc_bdr
> > > *tx_ring, struct sk_buff *skb)
> > > > dma_err:
> > > > dev_err(tx_ring->dev, "DMA map error");
> > > >
> > > > - do {
> > > > + while (count--) {
> > > > tx_swbd = &tx_ring->tx_swbd[i];
> > > > enetc_free_tx_frame(tx_ring, tx_swbd);
> > > > if (i == 0)
> > > > i = tx_ring->bd_count;
> > > > i--;
> > > > - } while (count--);
> > > > + };
> > >
> > > In enetc_lso_hw_offload() this is fixed by --count instead of changing
> > > to while and count--, maybe follow this scheme, or event better call
> > > helper function to fix in one place.
> >
> > The situation is slightly different in enetc_map_tx_buffs(), the count
> > may be 0 when the error occurs. But in enetc_lso_hw_offload(), the
> > count will not be 0 when the error occurs.
>
> Right, didn't see that, sorry.
>
> >
> > >
> > > The same problem is probably in enetc_map_tx_tso_buffs().
> > >
> >
> > I think there is no such problem in enetc_map_tx_tso_buffs(),
> > because the index 'i' has been increased before the error occurs,
> > but the count is not increased, so the actual 'count' is count + 1.
> >
>
> But you can reach the error code jumping to label "err_chained_bd" where
> both i and count is increased. Isn't it a problem?
>
You are right, I ignored this label. I will add a separate patch to fix this issue.
Thanks.
> BTW, not increasing i and count in one place looks like unnecessary
> complication ;) .
>
