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SubjectRe: [PATCH linux-next] net:stmmac: Fix the unsigned expression compared with zero
On Thu, Jul 15, 2021 at 10:12:04AM +0000, Joakim Zhang wrote:
>
> > -----Original Message-----
> > From: menglong8.dong@gmail.com <menglong8.dong@gmail.com>
> > Sent: 2021年7月15日 15:46
> > To: davem@davemloft.net
> > Cc: peppe.cavallaro@st.com; alexandre.torgue@foss.st.com;
> > joabreu@synopsys.com; kuba@kernel.org; mcoquelin.stm32@gmail.com;
> > netdev@vger.kernel.org; linux-stm32@st-md-mailman.stormreply.com;
> > linux-arm-kernel@lists.infradead.org; linux-kernel@vger.kernel.org; Zhang
> > Yunkai <zhang.yunkai@zte.com.cn>; Zeal Robot <zealci@zte.com.cn>
> > Subject: [PATCH linux-next] net:stmmac: Fix the unsigned expression compared
> > with zero
> >
> > From: Zhang Yunkai <zhang.yunkai@zte.com.cn>
> >
> > WARNING: Unsigned expression "queue" compared with zero.
> > Reported-by: Zeal Robot <zealci@zte.com.cn>
> > Signed-off-by: Zhang Yunkai <zhang.yunkai@zte.com.cn>
> > ---
> > drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 8 ++------
> > 1 file changed, 2 insertions(+), 6 deletions(-)
> >
> > diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > index 7b8404a21544..a4cf2c640531 100644
> > --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
> > @@ -1699,7 +1699,7 @@ static int init_dma_rx_desc_rings(struct net_device
> > *dev, gfp_t flags)
> > return 0;
> >
> > err_init_rx_buffers:
> > - while (queue >= 0) {
> > + do {
> > struct stmmac_rx_queue *rx_q = &priv->rx_queue[queue];
> >
> > if (rx_q->xsk_pool)
> > @@ -1710,11 +1710,7 @@ static int init_dma_rx_desc_rings(struct
> > net_device *dev, gfp_t flags)
> > rx_q->buf_alloc_num = 0;
> > rx_q->xsk_pool = NULL;
> >
> > - if (queue == 0)
> > - break;
> > -
> > - queue--;
> > - }
> > + } while (queue--);
> >
> > return ret;
> > }
>
>
> This is a real Coverity issue since queue variable is defined as u32, but there is no breakage from logic, it will break while loop when queue equal 0, and queue[0] actually need be handled.
> After your code change, queue[0] will not be handled, right? It will break the logic. If you want to fix the this issue, I think the easiest way is to define queue variable to int.
>
> Best Regards,
> Joakim Zhang
> > --
> > 2.25.1
>

The function '__init_dma_rx_desc_rings' is expecting 'queue' to be u32 type.
I would suggest the following:-

@@ -1686,6 +1686,7 @@ static int init_dma_rx_desc_rings(struct net_device *dev, gfp_t flags)
struct stmmac_priv *priv = netdev_priv(dev);
u32 rx_count = priv->plat->rx_queues_to_use;
u32 queue;
+ u32 i;
int ret;

/* RX INITIALIZATION */
@@ -1701,21 +1702,16 @@ static int init_dma_rx_desc_rings(struct net_device *dev, gfp_t flags)
return 0;

err_init_rx_buffers:
- while (queue >= 0) {
- struct stmmac_rx_queue *rx_q = &priv->rx_queue[queue];
+ for (i = 0; i <= queue; i++) {
+ struct stmmac_rx_queue *rx_q = &priv->rx_queue[i];

if (rx_q->xsk_pool)
- dma_free_rx_xskbufs(priv, queue);
+ dma_free_rx_xskbufs(priv, i);
else
- dma_free_rx_skbufs(priv, queue);
+ dma_free_rx_skbufs(priv, i);

rx_q->buf_alloc_num = 0;
rx_q->xsk_pool = NULL;
-
- if (queue == 0)
- break;
-
- queue--;
}

Regards,
VK
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