Re: [RFC 01/10] crypto: factor async completion for general use

[Gilad Ben-Yossef <gilad@benyossef.com>]

On Thu, May 11, 2017 at 11:09 AM, Eric Biggers <ebiggers3@gmail.com> wrote:
> On Thu, May 11, 2017 at 10:29:47AM +0300, Gilad Ben-Yossef wrote:
>> > With regards to the wait being uninterruptible, I agree that this should be the
>> > default behavior, because I think users waiting for specific crypto requests are
>> > generally not prepared to handle the wait actually being interrupted.  After
>> > interruption the crypto operation will still proceed in the background, and it
>> > will use buffers which the caller has in many cases already freed.  However, I'd
>> > suggest taking a close look at anything that was actually doing an interruptible
>> > wait before, to see whether it was a bug or intentional (or "doesn't matter").
>> >
>> > And yes there could always be a crypto_wait_req_interruptible() introduced if
>> > some users need it.
>>
>> So this one was a bit of a shocker.  I though the  _interruptible use
>> sites seemed
>> wrong in the sense of being needless. However, after reading your feedback and
>> reviewing the code I'm pretty sure every single one of them (including
>> the one I've
>> added in dm-verity-target.c this merge window)  are down right dangerous and
>> can cause random data corruption... so thanks for pointing this out!
>>
>> I though of this patch set as a "make the code pretty" for 4.13 kind
>> of patch set.
>> Looks like it's a bug fix now, maybe even stable material.
>>
>> Anyway, I'll roll a v2 and we'll see.
>>
>
> Any that are called only by kernel threads would theoretically be safe since
> kernel threads don't ordinarily receive signals.  But I think that at least the
> drbg and gcm waits can be reached by user threads, since they can be called via
> algif_rng and algif_aead respectively.
>
> I recommend putting any important fixes first, so they can be backported without
> depending on crypto_wait_req().
>

OK, I'll send out a separate bug fix series first and rebase the
crypto_wait one on top
of it then.

Thanks,
Gilad

-- 
Gilad Ben-Yossef
Chief Coffee Drinker

"If you take a class in large-scale robotics, can you end up in a
situation where the homework eats your dog?"
 -- Jean-Baptiste Queru