Re: [PATCH RESEND] hwrng: core - don't pass stack allocated buffer to rng->read()

[Laszlo Ersek]

On 10/21/16 23:04, Andy Lutomirski wrote:
> On Fri, Oct 21, 2016 at 1:48 PM, Laszlo Ersek <lersek@xxxxxxxxxx> wrote:
>> The virtio-rng backend for hwrng passes the buffer that it receives for
>> filling to sg_set_buf() directly, in:
>>
>> virtio_read()       [drivers/char/hw_random/virtio-rng.c]
>>   register_buffer() [drivers/char/hw_random/virtio-rng.c]
>>     sg_init_one()   [lib/scatterlist.c]
>>       sg_set_buf()  [include/linux/scatterlist.h]
>>
>> In turn, the sg_set_buf() function, when built with CONFIG_DEBUG_SG,
>> actively enforces (justifiedly) that the buffer used within the
>> scatter-gather list live in physically contiguous memory:
>>
>>   BUG_ON(!virt_addr_valid(buf));
>>
>> The combination of the above two facts means that whatever calls
>> virtio_read() -- via the hwrng.read() method -- has to allocate the
>> recipient buffer in physically contiguous memory.
> 
> Indeed.  This bug should be fixed by:
> 
> https://git.kernel.org/cgit/linux/kernel/git/herbert/cryptodev-2.6.git/commit/?id=6d4952d9d9d4dc2bb9c0255d95a09405a1e958f7
> 

Cool, thanks!

(My commit message is better tho ;))

Cheers
Laszlo