Re: [PATCH] crypto: api - Redo lookup on EEXIST

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

On 19.05.2025 12:29, Herbert Xu wrote:
> On Mon, May 19, 2025 at 10:09:10AM +0200, Ingo Franzki wrote:
>>
>> 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)
> 
> Please try this patch:

Since I can't reproduce the problem at will, I can't tell if your patch solves the problem. From what I can tell it looks reasonable. 
Nevertheless, I have added your patch to be applied on top of the next day's next kernel tree in our CI so that it runs with your patch for a while.
Lets run it for a few days and see if the error still shows up or not. 

> 
> ---8<---
> When two crypto algorithm lookups occur at the same time with
> different names for the same algorithm, e.g., ctr(aes-generic)
> and ctr(aes), they will both be instantiated.  However, only one
> of them can be registered.  The second instantiation will fail
> with EEXIST.
> 
> Avoid failing the second lookup by making it retry, but only once
> because there are tricky names such as gcm_base(ctr(aes),ghash)
> that will always fail, despite triggering instantiation and EEXIST.
> 
> Reported-by: Ingo Franzki <ifranzki@linux.ibm.com>
> Fixes: 2825982d9d66 ("[CRYPTO] api: Added event notification")
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
> 
> diff --git a/crypto/api.c b/crypto/api.c
> index 133d9b626922..5724d62e9d07 100644
> --- a/crypto/api.c
> +++ b/crypto/api.c
> @@ -219,10 +219,19 @@ static struct crypto_alg *crypto_larval_wait(struct crypto_alg *alg,
>  		if (crypto_is_test_larval(larval))
>  			crypto_larval_kill(larval);
>  		alg = ERR_PTR(-ETIMEDOUT);
> -	} else if (!alg) {
> +	} else if (!alg || PTR_ERR(alg) == -EEXIST) {
> +		int err = alg ? -EEXIST : -EAGAIN;
> +
> +		/*
> +		 * EEXIST is expected because two probes can be scheduled
> +		 * at the same time with one using alg_name and the other
> +		 * using driver_name.  Do a re-lookup but do not retry in
> +		 * case we hit a quirk like gcm_base(ctr(aes),...) which
> +		 * will never match.
> +		 */
>  		alg = &larval->alg;
>  		alg = crypto_alg_lookup(alg->cra_name, type, mask) ?:
> -		      ERR_PTR(-EAGAIN);
> +		      ERR_PTR(err);
>  	} else if (IS_ERR(alg))
>  		;
>  	else if (crypto_is_test_larval(larval) &&


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