linux-kernel - Re: [Part2 PATCH v6 16/38] crypto: ccp: Implement SEV_PEK

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Date:   Mon, 23 Oct 2017 07:15:30 -0500
From:   Brijesh Singh <brijesh.singh@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     brijesh.singh@....com, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Gary Hook <gary.hook@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [Part2 PATCH v6 16/38] crypto: ccp: Implement SEV_PEK_GEN ioctl
 command

On 10/23/17 4:32 AM, Borislav Petkov wrote:
...
>> +static int sev_ioctl_do_pek_pdh_gen(int cmd, struct sev_issue_cmd *argp)
>> +{
>> +	int ret, err;
>> +
>> +	ret = sev_platform_init(NULL, &argp->error);
>> +	if (ret)
>> +		return ret;
>> +
>> +	ret = sev_do_cmd(cmd, 0, &argp->error);
> So this ret value gets potentially overwritten here. You need
> to either handle the case properly when sev_do_cmd() fails and
> sev_platform_shutdown() gets to issue SEV_CMD_SHUTDOWN (i.e., when it
> gets overwritten), or not write into ret at all by initializing it to 0
> at function entry.
>

I am not sure if I am able to understand your feedback. The
sev_platform_shutdown() is called unconditionally.

1) if sev_do_cmd() fails and sev_platform_shutdown() was success then
'ret' will contain the  error code from sev_do_cmd().
2) if sev_do_cmd() was success but sev_platform_shutdown() fails then
'ret' will contain the error code from sev_platform_shutdown()
3) if both sev_do_cmd() and sev_platform_shutdown() fails then 'ret'
will contain error code from the sev_platform_shutdown().