Invalid assignment to gate in st21nfca_get_iso14443_3_uid

Invalid assignment to gate in st21nfca_get_iso14443_3_uid

[Nicolas Iooss]

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

[PATCH] NFC: st21nfca: fix st21nfca_get_iso14443_3_uid data copy

[Nicolas Iooss]

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 <nicolas.iooss_linux@m4x.org>
---

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

Re: [PATCH] NFC: st21nfca: fix st21nfca_get_iso14443_3_uid data copy

[Nicolas Iooss]

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 <nicolas.iooss_linux@m4x.org>
> ---
> 
> 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);
> 

Re: [PATCH] NFC: st21nfca: fix st21nfca_get_iso14443_3_uid data copy

[christophe.ricard]

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 <nicolas.iooss_linux@m4x.org>
>> ---
>>
>> 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);
>>