linux-kernel - Re: [PATCH v6 24/26] powerpc/pseries: Implement secvars for dynamic secure boot

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Message-ID: <a63276d5-1be4-b140-6a4a-4ad4efa60eda@linux.ibm.com>
Date:   Fri, 10 Feb 2023 16:28:40 -0500
From:   Stefan Berger <stefanb@...ux.ibm.com>
To:     Andrew Donnellan <ajd@...ux.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org, linux-integrity@...r.kernel.org
Cc:     sudhakar@...ux.ibm.com, erichte@...ux.ibm.com,
        gregkh@...uxfoundation.org, nayna@...ux.ibm.com, npiggin@...il.com,
        linux-kernel@...r.kernel.org, zohar@...ux.ibm.com,
        gjoyce@...ux.ibm.com, ruscur@...sell.cc, joel@....id.au,
        bgray@...ux.ibm.com, brking@...ux.ibm.com, gcwilson@...ux.ibm.com
Subject: Re: [PATCH v6 24/26] powerpc/pseries: Implement secvars for dynamic
 secure boot



On 2/10/23 16:23, Stefan Berger wrote:
> 
> 

>> +
>> +// PLPKS dynamic secure boot doesn't give us a format string in the same way OPAL does.
>> +// Instead, report the format using the SB_VERSION variable in the keystore.
>> +// The string is made up by us, and takes the form "ibm,plpks-sb-v<n>" (or "ibm,plpks-sb-unknown"
>> +// if the SB_VERSION variable doesn't exist). Hypervisor defines the SB_VERSION variable as a
>> +// "1 byte unsigned integer value".
>> +static ssize_t plpks_secvar_format(char *buf, size_t bufsize)
>> +{
>> +    struct plpks_var var = {0};
>> +    ssize_t ret;
>> +    u8 version;
>> +
>> +    var.component = NULL;
> 
> Since it's initialized with {0} this is not necessary.
> 
>> +    // Only the signed variables have null bytes in their names, this one doesn't
>> +    var.name = "SB_VERSION";
>> +    var.namelen = strlen(var.name);
>> +    var.datalen = 1;
>> +    var.data = &version;
>> +
>> +    // Unlike the other vars, SB_VERSION is owned by firmware instead of the OS
>> +    ret = plpks_read_fw_var(&var);
>> +    if (ret) {
>> +        if (ret == -ENOENT) {
>> +            ret = snprintf(buf, bufsize, "ibm,plpks-sb-unknown");
>> +        } else {
>> +            pr_err("Error %ld reading SB_VERSION from firmware\n", ret);
>> +            ret = -EIO;
>> +        }
>> +        goto err;
>> +    }
>> +
>> +    ret = snprintf(buf, bufsize, "ibm,plpks-sb-v%hhu", version);
>> +
>> +err:
>> +    kfree(var.data);
> 
> remove the kfree()

Actually don't remove it but it should probably be

if (var.data != &version)
     kfree(var.data);
> 
>> +    return ret;
>> +}
>> +