Hi Dan,
> The patch cfad1ba87150: "NFC: Initial support for Inside Secure
> microread" from Dec 18, 2012, leads to the following
> Sparse warning:
>
> drivers/nfc/microread/microread.c:534:25:
> warning: cast to restricted __le16"
>
> drivers/nfc/microread/microread.c
> 512 case MICROREAD_GATE_ID_MREAD_ISO_A_3:
> 513 targets->supported_protocols =
> 514 nfc_hci_sak_to_protocol(skb->data[MICROREAD_EMCF_A3_SAK]);
> 515 targets->sens_res =
> 516 be16_to_cpu(*(u16 *)&skb->data[MICROREAD_EMCF_A3_ATQA]);
> ^^^^^^^^^^^
> sens_res is network (big) endian here. We could silence the sparse
> warning by doing:
>
> argets->sens_res =
> ntohs(*(__be16 *)&skb->data[MICROREAD_EMCF_A3_ATQA]);
wouldn't it be easier to just use get_unaligned_be16. I am not even sure that we actually have a proper alignment on all architecture here. So this might be safer anyway. Eric?
>
> 517 targets->sel_res = skb->data[MICROREAD_EMCF_A3_SAK];
> 518 targets->nfcid1_len = skb->data[MICROREAD_EMCF_A3_LEN];
> 519 if (targets->nfcid1_len > sizeof(targets->nfcid1)) {
> 520 r = -EINVAL;
> 521 goto exit_free;
> 522 }
> 523 memcpy(targets->nfcid1, &skb->data[MICROREAD_EMCF_A3_UID],
> 524 targets->nfcid1_len);
> 525 break;
> 526 case MICROREAD_GATE_ID_MREAD_ISO_B:
> 527 targets->supported_protocols = NFC_PROTO_ISO14443_B_MASK;
> 528 memcpy(targets->nfcid1, &skb->data[MICROREAD_EMCF_B_UID], 4);
> 529 targets->nfcid1_len = 4;
> 530 break;
> 531 case MICROREAD_GATE_ID_MREAD_NFC_T1:
> 532 targets->supported_protocols = NFC_PROTO_JEWEL_MASK;
> 533 targets->sens_res =
> 534 le16_to_cpu(*(u16 *)&skb->data[MICROREAD_EMCF_T1_ATQA]);
> ^^^^^^^^^^^
> But here it is little endian. This seems like either a horrible
> protocol or a bug in the code.
>
> 535 memcpy(targets->nfcid1, &skb->data[MICROREAD_EMCF_T1_UID], 4);
> 536 targets->nfcid1_len = 4;
> 537 break;
>
> Btw, we also don't seem to check if we are reading beyond the end of
> skb->len. This would only be a problem if we got unlucky and skb->data
> were allocated at the end of page. The read beyond the end of the page
> would cause an oops.
Regards
Marcel
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