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From:   Horia Geanta <horia.geanta@nxp.com>
To:     Andrey Smirnov <andrew.smirnov@gmail.com>,
        "linux-crypto@vger.kernel.org" <linux-crypto@vger.kernel.org>
CC:     Chris Healy <cphealy@gmail.com>,
        Lucas Stach <l.stach@pengutronix.de>,
        Herbert Xu <herbert@gondor.apana.org.au>,
        Iuliana Prodan <iuliana.prodan@nxp.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        dl-linux-imx <linux-imx@nxp.com>
Subject: Re: [PATCH v7 6/9] crypto: caam - check if RNG job failed
Thread-Topic: [PATCH v7 6/9] crypto: caam - check if RNG job failed
Thread-Index: AQHV1TLUvWTrrHqD+kWSWumiFCRkzg==
Date:   Wed, 12 Feb 2020 10:41:21 +0000
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References: <20200127165646.19806-1-andrew.smirnov@gmail.com>
 <20200127165646.19806-7-andrew.smirnov@gmail.com>
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On 1/27/2020 6:57 PM, Andrey Smirnov wrote:=0A=
> @@ -60,12 +65,12 @@ static struct caam_rng_ctx *to_caam_rng_ctx(struct hw=
rng *r)=0A=
>  static void caam_rng_done(struct device *jrdev, u32 *desc, u32 err,=0A=
>  			  void *context)=0A=
>  {=0A=
> -	struct completion *done =3D context;=0A=
> +	struct caam_rng_job_ctx *jctx =3D context;=0A=
>  =0A=
>  	if (err)=0A=
> -		caam_jr_strstatus(jrdev, err);=0A=
> +		*jctx->err =3D caam_jr_strstatus(jrdev, err);=0A=
>  =0A=
> -	complete(done);=0A=
> +	complete(jctx->done);=0A=
>  }=0A=
>  =0A=
>  static u32 *caam_init_desc(u32 *desc, dma_addr_t dst_dma, int len)=0A=
> @@ -89,6 +94,10 @@ static int caam_rng_read_one(struct device *jrdev,=0A=
>  {=0A=
>  	dma_addr_t dst_dma;=0A=
>  	int err;=0A=
> +	struct caam_rng_job_ctx jctx =3D {=0A=
> +		.done =3D done,=0A=
> +		.err  =3D &err,=0A=
> +	};=0A=
>  =0A=
>  	len =3D min_t(int, len, CAAM_RNG_MAX_FIFO_STORE_SIZE);=0A=
>  =0A=
> @@ -101,7 +110,7 @@ static int caam_rng_read_one(struct device *jrdev,=0A=
>  	init_completion(done);=0A=
>  	err =3D caam_jr_enqueue(jrdev,=0A=
>  			      caam_init_desc(desc, dst_dma, len),=0A=
> -			      caam_rng_done, done);=0A=
> +			      caam_rng_done, &jctx);=0A=
AFAICT there's a race condition b/w caam_jr_enqueue() and caam_rng_done(),=
=0A=
both writing to "err":=0A=
caam_jr_enqueue()=0A=
	-> JR interrupt -> caam_jr_interrupt() -> tasklet_schedule()...=0A=
	-> spin_unlock_bh()=0A=
	-> caam_jr_dequeue() -> caam_rng_done() -> write err=0A=
	-> return 0 -> write err=0A=
=0A=
Horia=0A=