linux-kernel - Re: [PATCH 2/2] crypto: ccp - Fail the PSP initialization when writing psp data file failed

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Date:   Wed, 10 Aug 2022 15:37:25 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Jacky Li <jackyli@...gle.com>,
        Brijesh Singh <brijesh.singh@....com>,
        John Allen <john.allen@....com>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Marc Orr <marcorr@...gle.com>, Alper Gun <alpergun@...gle.com>,
        Peter Gonda <pgonda@...gle.com>, linux-crypto@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] crypto: ccp - Fail the PSP initialization when
 writing psp data file failed

On 8/2/22 13:55, Jacky Li wrote:
> Currently the OS continues the PSP initialization when there is a write
> failure to the init_ex_file. Therefore, the userspace would be told that
> SEV is properly INIT'd even though the psp data file is not updated.
> This is problematic because later when asked for the SEV data, the OS
> won't be able to provide it.
> 
> Fixes: 3d725965f836 ("crypto: ccp - Add SEV_INIT_EX support")
> Reported-by: Peter Gonda <pgonda@...gle.com>
> Signed-off-by: Jacky Li <jackyli@...gle.com>
> ---
>   drivers/crypto/ccp/sev-dev.c | 23 +++++++++++++----------
>   1 file changed, 13 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/crypto/ccp/sev-dev.c b/drivers/crypto/ccp/sev-dev.c
> index 5bb2ae250d38..fd6bb01eb198 100644
> --- a/drivers/crypto/ccp/sev-dev.c
> +++ b/drivers/crypto/ccp/sev-dev.c
> @@ -233,7 +233,7 @@ static int sev_read_init_ex_file(void)
>   	return 0;
>   }
>   
> -static void sev_write_init_ex_file(void)
> +static int sev_write_init_ex_file(void)
>   {
>   	struct sev_device *sev = psp_master->sev_data;
>   	struct file *fp;
> @@ -243,14 +243,15 @@ static void sev_write_init_ex_file(void)
>   	lockdep_assert_held(&sev_cmd_mutex);
>   
>   	if (!sev_init_ex_buffer)
> -		return;
> +		return 0;
>   
>   	fp = open_file_as_root(init_ex_path, O_CREAT | O_WRONLY, 0600);
>   	if (IS_ERR(fp)) {
> +		int ret = PTR_ERR(fp);

Please put a blank line after the variable declaration.

>   		dev_err(sev->dev,
>   			"SEV: could not open file for write, error %ld\n",
> -			PTR_ERR(fp));
> -		return;
> +			ret);

You'll need to fix the kernel test robot report here.

Thanks,
Tom

> +		return ret;
>   	}
>   
>   	nwrite = kernel_write(fp, sev_init_ex_buffer, NV_LENGTH, &offset);
> @@ -261,18 +262,20 @@ static void sev_write_init_ex_file(void)
>   		dev_err(sev->dev,
>   			"SEV: failed to write %u bytes to non volatile memory area, ret %ld\n",
>   			NV_LENGTH, nwrite);
> -		return;
> +		return -EIO;
>   	}
>   
>   	dev_dbg(sev->dev, "SEV: write successful to NV file\n");
> +
> +	return 0;
>   }
>   
> -static void sev_write_init_ex_file_if_required(int cmd_id)
> +static int sev_write_init_ex_file_if_required(int cmd_id)
>   {
>   	lockdep_assert_held(&sev_cmd_mutex);
>   
>   	if (!sev_init_ex_buffer)
> -		return;
> +		return 0;
>   
>   	/*
>   	 * Only a few platform commands modify the SPI/NV area, but none of the
> @@ -287,10 +290,10 @@ static void sev_write_init_ex_file_if_required(int cmd_id)
>   	case SEV_CMD_PEK_GEN:
>   		break;
>   	default:
> -		return;
> +		return 0;
>   	}
>   
> -	sev_write_init_ex_file();
> +	return sev_write_init_ex_file();
>   }
>   
>   static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
> @@ -363,7 +366,7 @@ static int __sev_do_cmd_locked(int cmd, void *data, int *psp_ret)
>   			cmd, reg & PSP_CMDRESP_ERR_MASK);
>   		ret = -EIO;
>   	} else {
> -		sev_write_init_ex_file_if_required(cmd);
> +		ret = sev_write_init_ex_file_if_required(cmd);
>   	}
>   
>   	print_hex_dump_debug("(out): ", DUMP_PREFIX_OFFSET, 16, 2, data,