On Thu, Aug 25, 2022 at 9:10 AM Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
>
> Hello Rob Clark,
>
> The patch 4165cf7ba52a: "wcn36xx: check dma_mapping_error()" from Jul
> 3, 2017, leads to the following Smatch static checker warning:
>
> drivers/net/wireless/ath/wcn36xx/dxe.c:305 wcn36xx_dxe_fill_skb()
> warn: 'dxe->dst_addr_l' is not a DMA mapping error
>
> drivers/net/wireless/ath/wcn36xx/dxe.c:805 wcn36xx_dxe_tx_frame()
> warn: 'desc_skb->src_addr_l' is not a DMA mapping error
>
> drivers/net/wireless/ath/wcn36xx/dxe.c
> 290 static int wcn36xx_dxe_fill_skb(struct device *dev,
> 291 struct wcn36xx_dxe_ctl *ctl,
> 292 gfp_t gfp)
> 293 {
> 294 struct wcn36xx_dxe_desc *dxe = ctl->desc;
> 295 struct sk_buff *skb;
> 296
> 297 skb = alloc_skb(WCN36XX_PKT_SIZE, gfp);
> 298 if (skb == NULL)
> 299 return -ENOMEM;
> 300
> 301 dxe->dst_addr_l = dma_map_single(dev,
> 302 skb_tail_pointer(skb),
> 303 WCN36XX_PKT_SIZE,
> 304 DMA_FROM_DEVICE);
> --> 305 if (dma_mapping_error(dev, dxe->dst_addr_l)) {
>
> I'm so surprised that adding this check fixed a bug. There is an
> addr_l and addr_h (presumably for the low and high bits of the address?)
> The ->dst_addr_h is never used.
>
> A 32bit dst_addr_l can't be equal to DMA_MAPPING_ERROR unless it's a 32
> bit system-ish.
judging by the date, it was probably on a 32b system ;-)
that said, it doesn't seem like that code even supports systems w/ 64b dma addr
BR,
-R
>
> 306 dev_err(dev, "unable to map skb\n");
> 307 kfree_skb(skb);
> 308 return -ENOMEM;
> 309 }
> 310 ctl->skb = skb;
> 311
> 312 return 0;
> 313 }
>
> regards,
> dan carpenter
