Re: [PATCH] Add Ingenic JZ4780 hardware RNG driver

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Thu, Aug 18, 2016 at 10:44:18AM +0530, PrasannaKumar Muralidharan wrote:
> >> +static int jz4780_rng_read(struct hwrng *rng, void *buf, size_t max, bool wait)
> >> +{
> >> +     struct jz4780_rng *jz4780_rng = container_of(rng, struct jz4780_rng,
> >> +                                                     rng);
> >> +     u32 *data = buf;
> >> +     *data = jz4780_rng_readl(jz4780_rng, REG_RNG_DATA);
> >> +     return 4;
> >> +}
> >
> > If max is less than 4, its bad
> 
> Data will be 4 bytes.
> 

No, according to comment in include/linux/hw_random.h "drivers can fill up to max bytes of data"
So you cannot write more than max bytes without risking buffer overflow.

And if max > 4, hwrng client need to recall your read function.
The better example I found is tpm_get_random() in drivers/char/tpm/tpm-interface.c for handling both problem.

Regards

--
To unsubscribe from this list: send the line "unsubscribe linux-crypto" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html



[Index of Archives]     [Kernel]     [Gnu Classpath]     [Gnu Crypto]     [DM Crypt]     [Netfilter]     [Bugtraq]

  Powered by Linux