linux-kernel - Re: [PATCH 2/4] crypto: drbg wait for crypto op not signal safe

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Date:   Tue, 16 May 2017 15:39:46 -0700
From:   Eric Biggers <ebiggers3@...il.com>
To:     Gilad Ben-Yossef <gilad@...yossef.com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Jonathan Corbet <corbet@....net>,
        David Howells <dhowells@...hat.com>,
        Ofir Drang <ofir.drang@....com>,
        Gilad Ben-Yossef <gilad.benyossef@....com>,
        stable@...r.kernel.org, linux-crypto@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        keyrings@...r.kernel.org
Subject: Re: [PATCH 2/4] crypto: drbg wait for crypto op not signal safe

Hi Gilad,

On Thu, May 11, 2017 at 02:53:43PM +0300, Gilad Ben-Yossef wrote:
> drbg_kcapi_sym_ctr() was using wait_for_completion_interruptible() to
> wait for completion of async crypto op but if a signal occurs it
> may return before DMA ops of HW crypto provider finish, thus
> corrupting the output buffer.
> 
> Resolve this by using wait_for_completion() instead.
> 
> Reported-by: Eric Biggers <ebiggers3@...il.com>
> Signed-off-by: Gilad Ben-Yossef <gilad@...yossef.com>
> CC: stable@...r.kernel.org
> ---
>  crypto/drbg.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
> 
> diff --git a/crypto/drbg.c b/crypto/drbg.c
> index fa749f4..fa9054d 100644
> --- a/crypto/drbg.c
> +++ b/crypto/drbg.c
> @@ -1767,8 +1767,7 @@ static int drbg_kcapi_sym_ctr(struct drbg_state *drbg,
>  			break;
>  		case -EINPROGRESS:
>  		case -EBUSY:
> -			ret = wait_for_completion_interruptible(
> -				&drbg->ctr_completion);
> +			ret = wait_for_completion(&drbg->ctr_completion);
>  			if (!ret && !drbg->ctr_async_err) {
>  				reinit_completion(&drbg->ctr_completion);
>  				break;
> -- 

wait_for_completion() doesn't return a value.  This was fixed in the next patch,
but it should be done in this patch.

Eric