Sporadic errors with alg selftest on next kernel.

[Ingo Franzki <ifranzki@linux.ibm.com>]

Hi Herbert,

besides the regression found in paes-crt on s390x (reported and analyzed by Harald already), we sporadically encounter additional strange failures in our CI on the next kernel:

During this weekend's CI run, we got the following:

    alg: aead: error allocating gcm_base(ctr(aes-generic),ghash-generic) (generic impl of gcm(aes)): -17
    alg: self-tests for gcm(aes) using gcm-aes-s390 failed (rc=-17)

Last week, we had a similar failure:

    aes_s390: Allocating AES fallback algorithm ctr(aes) failed
    alg: skcipher: failed to allocate transform for ctr-aes-s390: -17
    alg: self-tests for ctr(aes) using ctr-aes-s390 failed (rc=-17)

Those are only single failures, not reproducible, happen only of one system, although the same code is run on multiple systems.
So it must be some kind a race condition...

-17 is EEXIST, and from a quick look into the code this might be coming from registering an alg (e.g. __crypto_register_alg(), crypto_register_template(), af_alg_register_type(), crypto_add_alg()) when the alg is already there....
So looks like one wants to register the same alg although it was already registered concurrently? 

Note that the s390x-AES ciphers are usually added via module_cpu_feature_match() automatically.
Maybe a selftest run attempts to add them again while or during aes_s390_init() is about to add them as well?

Its hard to debug, since it only happens sporadically and can't be reproduced easily.

Any idea where this might come from? 
We did not see these kind of errors since long time, and still don't see them on kernels other than next. 

Kind regards,
Ingo

-- 
Ingo Franzki
eMail: ifranzki@linux.ibm.com  
Tel: ++49 (0)7031-16-4648
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