linux-kernel - Re: [PATCH] crypto: iaa - Fix race condition when probing IAA devices

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Message-ID: <aEjnbdoqzLoMifRn@gondor.apana.org.au>
Date: Wed, 11 Jun 2025 10:18:21 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Vinicius Costa Gomes <vinicius.gomes@...el.com>
Cc: Kristen Accardi <kristen.c.accardi@...el.com>,
	"David S. Miller" <davem@...emloft.net>,
	Tom Zanussi <tom.zanussi@...ux.intel.com>,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] crypto: iaa - Fix race condition when probing IAA devices

On Tue, Jun 03, 2025 at 04:55:31PM -0700, Vinicius Costa Gomes wrote:
>
> diff --git a/drivers/crypto/intel/iaa/iaa_crypto_main.c b/drivers/crypto/intel/iaa/iaa_crypto_main.c
> index 23f585219fb4..2185c101bef3 100644
> --- a/drivers/crypto/intel/iaa/iaa_crypto_main.c
> +++ b/drivers/crypto/intel/iaa/iaa_crypto_main.c
> @@ -35,28 +35,39 @@ static unsigned int cpus_per_iaa;
>  
>  /* Per-cpu lookup table for balanced wqs */
>  static struct wq_table_entry __percpu *wq_table;
> +static DEFINE_SPINLOCK(wq_table_lock);

This can be called in BH context so you need to disable BH when
taking the spinlock.

>  static struct idxd_wq *wq_table_next_wq(int cpu)
>  {
> -	struct wq_table_entry *entry = per_cpu_ptr(wq_table, cpu);
> +	struct wq_table_entry *entry;
> +	struct idxd_wq *wq;
> +	int id;
> +
> +	guard(spinlock)(&wq_table_lock);
> +
> +	entry = per_cpu_ptr(wq_table, cpu);

You're taking a global spinlock around a per-cpu variable.  In that
case you might as well get rid of the per-cpu variable and use the
spinlock only.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt