linux-kernel - Re: [PATCH v2 7/8] crypto: ccp: Use the stack and common buffer for INIT command

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Date:   Wed, 7 Apr 2021 07:20:11 +0200
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Brijesh Singh <brijesh.singh@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        John Allen <john.allen@....com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH v2 7/8] crypto: ccp: Use the stack and common buffer for
 INIT command



Le 07/04/2021 à 00:49, Sean Christopherson a écrit :
> Drop the dedicated init_cmd_buf and instead use a local variable.  Now
> that the low level helper uses an internal buffer for all commands,
> using the stack for the upper layers is safe even when running with
> CONFIG_VMAP_STACK=y.
> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>   drivers/crypto/ccp/sev-dev.c | 10 ++++++----
>   drivers/crypto/ccp/sev-dev.h |  1 -
>   2 files changed, 6 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index e54774b0d637..9ff28df03030 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -233,6 +233,7 @@ static int sev_do_cmd(int cmd, void *data, int *psp_ret)
>   static int __sev_platform_init_locked(int *error)
>   {
>   	struct psp_device *psp = psp_master;
> +	struct sev_data_init data;

struct sev_data_init data = {0, 0, 0, 0};

>   	struct sev_device *sev;
>   	int rc = 0;
>   
> @@ -244,6 +245,7 @@ static int __sev_platform_init_locked(int *error)
>   	if (sev->state == SEV_STATE_INIT)
>   		return 0;
>   
> +	memset(&data, 0, sizeof(data));

Not needed.

>   	if (sev_es_tmr) {
>   		u64 tmr_pa;
>   
> @@ -253,12 +255,12 @@ static int __sev_platform_init_locked(int *error)
>   		 */
>   		tmr_pa = __pa(sev_es_tmr);
>   
> -		sev->init_cmd_buf.flags |= SEV_INIT_FLAGS_SEV_ES;
> -		sev->init_cmd_buf.tmr_address = tmr_pa;
> -		sev->init_cmd_buf.tmr_len = SEV_ES_TMR_SIZE;
> +		data.flags |= SEV_INIT_FLAGS_SEV_ES;
> +		data.tmr_address = tmr_pa;
> +		data.tmr_len = SEV_ES_TMR_SIZE;
>   	}
>   
> -	rc = __sev_do_cmd_locked(SEV_CMD_INIT, &sev->init_cmd_buf, error);
> +	rc = __sev_do_cmd_locked(SEV_CMD_INIT, &data, error);
>   	if (rc)
>   		return rc;
>   
> diff --git a/drivers/crypto/ccp/sev-dev.h b/drivers/crypto/ccp/sev-dev.h
> index 0fd21433f627..666c21eb81ab 100644
> --- a/drivers/crypto/ccp/sev-dev.h
> +++ b/drivers/crypto/ccp/sev-dev.h
> @@ -46,7 +46,6 @@ struct sev_device {
>   	unsigned int int_rcvd;
>   	wait_queue_head_t int_queue;
>   	struct sev_misc_dev *misc;
> -	struct sev_data_init init_cmd_buf;
>   
>   	u8 api_major;
>   	u8 api_minor;
>