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

From	Laszlo Ersek <lersek@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH RESEND] hwrng: core - don't pass stack allocated buffer to rng->read()
Date	2016-10-21 23:40 +0200
Message-ID	<suPHH-2MQ-17@gated-at.bofh.it> (permalink)
References	<suOVj-2gP-1@gated-at.bofh.it> <suPeG-2CB-13@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 10/21/16 23:04, Andy Lutomirski wrote:
> On Fri, Oct 21, 2016 at 1:48 PM, Laszlo Ersek <lersek@redhat.com> 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

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[PATCH RESEND] hwrng: core - don't pass stack allocated buffer to rng->read() Laszlo Ersek <lersek@redhat.com> - 2016-10-21 22:50 +0200
  Re: [PATCH RESEND] hwrng: core - don't pass stack allocated buffer to rng->read() Andy Lutomirski <luto@amacapital.net> - 2016-10-21 23:10 +0200
    Re: [PATCH RESEND] hwrng: core - don't pass stack allocated buffer  to rng->read() "Richard W.M. Jones" <rjones@redhat.com> - 2016-10-21 23:20 +0200
      Re: [PATCH RESEND] hwrng: core - don't pass stack allocated buffer to  rng->read() Laszlo Ersek <lersek@redhat.com> - 2016-10-21 23:40 +0200
    Re: [PATCH RESEND] hwrng: core - don't pass stack allocated buffer to  rng->read() Laszlo Ersek <lersek@redhat.com> - 2016-10-21 23:40 +0200

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