Hello,
While compiling Linux with -Wunused-but-set-parameter, gcc reported a
warning in st21nfca_get_iso14443_3_uid function, about "gate" being set
but not used [1]. By looking at the code, it is clear that "gate =
uid_skb->data;" does nothing useful. The function is only called once,
by st21nfca_hci_target_from_gate [2], which uses the content of the uid
array which is NOT initialized by st21nfca_get_iso14443_3_uid as the
source of a memcpy [3].
My understanding of the code is that "gate = uid_skb->data;" in
st21nfca_get_iso14443_3_uid should be changed to "memcpy(gate,
uid_skb->data, uid_skb->len);".
I'm new to the NFC subsystem so I can be wrong, in which case please
tell me what I missed in my analysis. Please Cc me when replying as I
am not subscribed to the mailing lists.
Thanks,
Nicolas
[1]
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/nfc/st21nfca/st21nfca.c?id=v4.0-rc1#n575
[2]
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/nfc/st21nfca/st21nfca.c?id=v4.0-rc1#n646
[3]
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/drivers/nfc/st21nfca/st21nfca.c?id=v4.0-rc1#n682
Hello,
I have not received any comments about this patch so I'm sending it
again. Could you please review it?
Nicolas
On 03/03/2015 12:58 PM, Nicolas Iooss wrote:
> st21nfca_get_iso14443_3_uid() does not correctly copy the uid from
> uid_skb->data to its gate parameter. "gate = uid_skb->data;" only puts
> a pointer to uid_skb->data to the local variable gate. This means that
> in st21nfca_hci_target_from_gate() the content of "u8
> uid[NFC_NFCID1_MAXSIZE]" local variable is never initialized before
> being used in memcpy(target->nfcid1, uid, len).
>
> Fix this by replacing the local variable assignment with a memcpy.
>
> This was found by compiling Linux with "gcc -Wunused-but-set-parameter".
>
> Signed-off-by: Nicolas Iooss <[email protected]>
> ---
>
> As I did not get any reply from https://lkml.org/lkml/2015/2/28/25 and
> got confirmation by other people that this may be a real bug, I am now
> sending a patch to fix it.
>
> drivers/nfc/st21nfca/st21nfca.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/nfc/st21nfca/st21nfca.c b/drivers/nfc/st21nfca/st21nfca.c
> index 24d3d240d5f4..ff70d2838b29 100644
> --- a/drivers/nfc/st21nfca/st21nfca.c
> +++ b/drivers/nfc/st21nfca/st21nfca.c
> @@ -588,7 +588,7 @@ static int st21nfca_get_iso14443_3_uid(struct nfc_hci_dev *hdev, u8 *gate,
> goto exit;
> }
>
> - gate = uid_skb->data;
> + memcpy(gate, uid_skb->data, uid_skb->len);
> *len = uid_skb->len;
> exit:
> kfree_skb(uid_skb);
>
st21nfca_get_iso14443_3_uid() does not correctly copy the uid from
uid_skb->data to its gate parameter. "gate = uid_skb->data;" only puts
a pointer to uid_skb->data to the local variable gate. This means that
in st21nfca_hci_target_from_gate() the content of "u8
uid[NFC_NFCID1_MAXSIZE]" local variable is never initialized before
being used in memcpy(target->nfcid1, uid, len).
Fix this by replacing the local variable assignment with a memcpy.
This was found by compiling Linux with "gcc -Wunused-but-set-parameter".
Signed-off-by: Nicolas Iooss <[email protected]>
---
As I did not get any reply from https://lkml.org/lkml/2015/2/28/25 and
got confirmation by other people that this may be a real bug, I am now
sending a patch to fix it.
drivers/nfc/st21nfca/st21nfca.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/nfc/st21nfca/st21nfca.c b/drivers/nfc/st21nfca/st21nfca.c
index 24d3d240d5f4..ff70d2838b29 100644
--- a/drivers/nfc/st21nfca/st21nfca.c
+++ b/drivers/nfc/st21nfca/st21nfca.c
@@ -588,7 +588,7 @@ static int st21nfca_get_iso14443_3_uid(struct nfc_hci_dev *hdev, u8 *gate,
goto exit;
}
- gate = uid_skb->data;
+ memcpy(gate, uid_skb->data, uid_skb->len);
*len = uid_skb->len;
exit:
kfree_skb(uid_skb);
--
2.3.1
Hi Nicolas,
Sorry for the late reply.
I am planning to include your patch with a Acked-by in a future patch serie.
Thanks a lot
Best Regards
Christophe
On 16/03/2015 13:28, Nicolas Iooss wrote:
> Hello,
> I have not received any comments about this patch so I'm sending it
> again. Could you please review it?
>
> Nicolas
>
> On 03/03/2015 12:58 PM, Nicolas Iooss wrote:
>> st21nfca_get_iso14443_3_uid() does not correctly copy the uid from
>> uid_skb->data to its gate parameter. "gate = uid_skb->data;" only puts
>> a pointer to uid_skb->data to the local variable gate. This means that
>> in st21nfca_hci_target_from_gate() the content of "u8
>> uid[NFC_NFCID1_MAXSIZE]" local variable is never initialized before
>> being used in memcpy(target->nfcid1, uid, len).
>>
>> Fix this by replacing the local variable assignment with a memcpy.
>>
>> This was found by compiling Linux with "gcc -Wunused-but-set-parameter".
>>
>> Signed-off-by: Nicolas Iooss <[email protected]>
>> ---
>>
>> As I did not get any reply from https://lkml.org/lkml/2015/2/28/25 and
>> got confirmation by other people that this may be a real bug, I am now
>> sending a patch to fix it.
>>
>> drivers/nfc/st21nfca/st21nfca.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/nfc/st21nfca/st21nfca.c b/drivers/nfc/st21nfca/st21nfca.c
>> index 24d3d240d5f4..ff70d2838b29 100644
>> --- a/drivers/nfc/st21nfca/st21nfca.c
>> +++ b/drivers/nfc/st21nfca/st21nfca.c
>> @@ -588,7 +588,7 @@ static int st21nfca_get_iso14443_3_uid(struct nfc_hci_dev *hdev, u8 *gate,
>> goto exit;
>> }
>>
>> - gate = uid_skb->data;
>> + memcpy(gate, uid_skb->data, uid_skb->len);
>> *len = uid_skb->len;
>> exit:
>> kfree_skb(uid_skb);
>>