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Oliver Hartkopp wrote:
> Marc Kleine-Budde wrote:
>> Oliver Hartkopp wrote:
>
>>>>> + *cf = (struct can_frame *)skb_put(skb, sizeof(struct can_frame));
>>> This could be also the place, where we could memset the struct can_frame to
>>> zero, right?
>>> Maybe we should do it here and leave it in alloc_can_err_skb() ...
>> In my at91 driver I don't need the memset, because I unconditionally
>> read the two 32 bit registers and write it into the ->data of the can_frame.
>>
>>>>> +
>>>>> + return skb;
>>>>> +}
>>>>> +EXPORT_SYMBOL_GPL(alloc_can_skb);
>>>>> +struct sk_buff *alloc_can_err_skb(struct net_device *dev, struct
>>>>> can_frame **cf)
>>>>> +{
>>>>> + struct sk_buff *skb;
>>>>> +
>>>>> + skb = alloc_can_skb(dev, cf);
>>>>> + if (unlikely(!skb))
>>>>> + return NULL;
>>>>> +
>>>>> + memset(*cf, 0, sizeof(struct can_frame));
>>> here :-)
>> Here we need zeroed ->data
>
> Ok, but if we think about some improvement, i would suggest to zero only the 8
> bytes data[] and leave the rest as-is.
>
> Maybe by setting the u64 casted data[] to zero.
yes, but we might still leak the 3 padding bytes...
>>>>> + (*cf)->can_id = CAN_ERR_FLAG;
>>>>> + (*cf)->can_dlc = CAN_ERR_DLC;
>
> As you can see, the can_id and the can_dlc is written anyway.
> When data[] is uninitialized, we expose 8-11 Bytes of uninitialized contiguous
> data to the userspace, when can_dlc=0 - i don't know if this is relevant.
In the can error frame use case we need data[] to be zero, because
usually bits are or'ed into the data[].
When looking at the normal rx path the driver might not need it....(as
the at91), unconditionally cleaning everything might make other drivers
simpler.
I doubt that we can measure the performance impact if we generally
memset the whole can frame, for both error and normal frames. So make it
clean ;)
cheers, Marc
- --
Pengutronix e.K. | Marc Kleine-Budde |
Linux Solutions for Science and Industry | Phone: +49-231-2826-924 |
Vertretung West/Dortmund | Fax: +49-5121-206917-5555 |
Amtsgericht Hildesheim, HRA 2686 | http://www.pengutronix.de |
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