Thread sanitiser problems

[Dr Paul Dale]

Yes, I’m mostly talking about #9454 here.  #9455 is a bug (clearing the flush flag after flushing not before).  The fix in #9477 addresses this and also removes the dependence on RAND_bytes.

The #9454 description includes thread sanitisizer logs showing different lock orderings — this has the potential to dead lock.  Agreed with Rich that giving up the lock would make sense, but I don’t see a way for this to be easily done.

That this also involves the RAND subsystem could be coincidental.  The other stack trace is getting an MD via a digest operation (i.e. both traces are for algorithms that use other algorithms).  The locks in question are the provider store lock and the context lock.

crypto/context.c:
    OPENSSL_CTX *ctx; /* function argument */
    CRYPTO_THREAD_read_lock(ctx->oncelock);

crypto/provider_core.c:
    OPENSSL_CTX *ctx; /* function argument */
    struct provider_store_st *store = get_provider_store(ctx);
    CRYPTO_THREAD_read_lock(store->lock);


Pauli
-- 
Dr Paul Dale | Cryptographer | Network Security & Encryption 
Phone +61 7 3031 7217
Oracle Australia



> On 30 Jul 2019, at 8:52 pm, Matthias St. Pierre <Matthias.St.Pierre at ncp-e.com> wrote:
> 
> Sorry, my reply was misleading, since Pauli is talking mainly about #9454.
> Please take a look at the issue description
> 
> https://github.com/openssl/openssl/issues/9454
> 
> instead.
> 
> Matthias
> 
> 
> 
> On 30.07.19 12:47, Matthias St. Pierre wrote:
>> 
>> 
>> On 30.07.19 12:43, Kurt Roeckx wrote:
>>> 
>>> I currently fail to see how that's a problem, unless that
>>> EVP_CIPHER_CTX tries to use a DRBG.
>> 
>> This is what I mean when I say that things have gotten more complicated under the hood
>> due to the replumbing. To understand the problem, please take at a look of the sanitizer
>> callstack in
>> 
>> https://github.com/openssl/openssl/issues/9455
>> 
>> 
>> Matthias
>> 
>> 
>> 
>