Re: [PATCH v8 22/30] pc-bios/s390-ccw: Add additional security checks for secure boot

[Zhuoying Cai <zycai@linux.ibm.com>]

On 3/2/26 6:24 AM, Thomas Huth wrote:
> On 12/02/2026 21.43, Zhuoying Cai wrote:
>> Add additional checks to ensure that components do not overlap with
>> signed components when loaded into memory.
>>
>> Add additional checks to ensure the load addresses of unsigned components
>> are greater than or equal to 0x2000.
>>
>> When the secure IPL code loading attributes facility (SCLAF) is installed,
>> all signed components must contain a secure code loading attributes block
>> (SCLAB).
>>
>> The SCLAB provides further validation of information on where to load the
>> signed binary code from the load device, and where to start the execution
>> of the loaded OS code.
>>
>> When SCLAF is installed, its content must be evaluated during secure IPL.
>> However, a missing SCLAB will not be reported in audit mode. The SCALB
>> checking will be skipped in this case.
>>
>> Add IPL Information Error Indicators (IIEI) and Component Error
>> Indicators (CEI) for IPL Information Report Block (IIRB).
>>
>> When SCLAF is installed, additional secure boot checks are performed
>> during zipl and store results of verification into IIRB.
>>
>> Signed-off-by: Zhuoying Cai <zycai@linux.ibm.com>
>> ---
>>   include/hw/s390x/ipl/qipl.h   |  29 +++-
>>   pc-bios/s390-ccw/s390-ccw.h   |   1 +
>>   pc-bios/s390-ccw/sclp.c       |   8 +
>>   pc-bios/s390-ccw/sclp.h       |   1 +
>>   pc-bios/s390-ccw/secure-ipl.c | 318 +++++++++++++++++++++++++++++++++-
>>   pc-bios/s390-ccw/secure-ipl.h |  42 +++++
>>   6 files changed, 395 insertions(+), 4 deletions(-)
> ...
>> diff --git a/pc-bios/s390-ccw/sclp.h b/pc-bios/s390-ccw/sclp.h
>> index cf147f4634..3441020d6b 100644
>> --- a/pc-bios/s390-ccw/sclp.h
>> +++ b/pc-bios/s390-ccw/sclp.h
>> @@ -52,6 +52,7 @@ typedef struct SCCBHeader {
>>   #define SCCB_DATA_LEN (SCCB_SIZE - sizeof(SCCBHeader))
>>   #define SCCB_FAC134_DIAG320_BIT 0x4
>>   #define SCCB_FAC_IPL_SIPL_BIT 0x4000
>> +#define SCCB_FAC_IPL_SCLAF_BIT 0x1000
>>   
>>   typedef struct ReadInfo {
>>       SCCBHeader h;
>> diff --git a/pc-bios/s390-ccw/secure-ipl.c b/pc-bios/s390-ccw/secure-ipl.c
>> index 27d2833642..54e41ec11c 100644
>> --- a/pc-bios/s390-ccw/secure-ipl.c
>> +++ b/pc-bios/s390-ccw/secure-ipl.c
>> @@ -197,6 +197,12 @@ static bool secure_ipl_supported(void)
>>           return false;
>>       }
>>   
>> +    if (!sclp_is_sclaf_on()) {
>> +        puts("Secure IPL Code Loading Attributes Facility is not supported by"
>> +             " the hypervisor!");
>> +        return false;
>> +    }
> 
> Let me double-check: This emits a warning and then the bios might continue 
> with the boot process with another device? (zipl_load() prints another 
> warning and returns without panic'ing when ipl_scsi() failed)
> 
> ... is this what we want? Or should the boot process be stopped in case 
> we're running in (non-audit) secure mode?
> 

Thanks for pointing this out.

I agree that the boot process shouldn’t continue in this situation. All
secure‑boot facilities need to be present so the required checks can
run; if anything is missing, falling back to another device wouldn’t
make sense because no security checks could be performed.

So the boot process should stop rather than continue, whether we’re in
audit or secure mode. I’ll update this in the next version.

>>       return true;
>>   }
>>   
>> @@ -259,6 +265,290 @@ static void addr_overlap_check(SecureIplCompAddrRange *comp_addr_range,
>>       *addr_range_index += 1;
>>   }
>>   
>> +static void check_unsigned_addr(uint64_t load_addr, IplDeviceComponentEntry *comp_entry)
>> +{
>> +    /* unsigned load address must be greater than or equal to 0x2000 */
>> +    if (load_addr >= 0x2000) {
>> +        return;
>> +    }
>> +
>> +    set_comp_cei_with_log(comp_entry, S390_CEI_INVALID_UNSIGNED_ADDR,
>> +                          "Load address is less than 0x2000");
>> +}
>> +
>> +static bool check_sclab_presence(uint8_t *sclab_magic,
>> +                                 IplDeviceComponentEntry *comp_entry)
>> +{
>> +    /* identifies the presence of SCLAB */
>> +    if (magic_match(sclab_magic, ZIPL_MAGIC)) {
>> +        return true;
>> +    }
>> +
>> +    if (comp_entry) {
>> +        comp_entry->cei |= S390_CEI_INVALID_SCLAB;
>> +    }
>> +
>> +    /* a missing SCLAB will not be reported in audit mode */
>> +    return false;
>> +}
>> +

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