Re: [PATCH] s390x/ipl: check kernel command line size

[Marc Hartmayer <mhartmay@linux.ibm.com>]

Thomas Huth <thuth@redhat.com> writes:

> On 06/10/2021 11.26, Marc Hartmayer wrote:
>> Check if the provided kernel command line exceeds the maximum size of the s390x
>> Linux kernel command line size, which is 896 bytes.
>> 
>> Reported-by: Sven Schnelle <svens@linux.ibm.com>
>> Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
>> ---
>>   hw/s390x/ipl.c | 12 +++++++++++-
>>   1 file changed, 11 insertions(+), 1 deletion(-)
>> 
>> diff --git a/hw/s390x/ipl.c b/hw/s390x/ipl.c
>> index 1821c6faeef3..a58ea58cc736 100644
>> --- a/hw/s390x/ipl.c
>> +++ b/hw/s390x/ipl.c
>> @@ -38,6 +38,7 @@
>>   #define KERN_IMAGE_START                0x010000UL
>>   #define LINUX_MAGIC_ADDR                0x010008UL
>>   #define KERN_PARM_AREA                  0x010480UL
>> +#define KERN_PARM_AREA_SIZE             0x000380UL
>>   #define INITRD_START                    0x800000UL
>>   #define INITRD_PARM_START               0x010408UL
>>   #define PARMFILE_START                  0x001000UL
>> @@ -190,10 +191,19 @@ static void s390_ipl_realize(DeviceState *dev, Error **errp)
>>            * loader) and it won't work. For this case we force it to 0x10000, too.
>>            */
>>           if (pentry == KERN_IMAGE_START || pentry == 0x800) {
>> -            char *parm_area = rom_ptr(KERN_PARM_AREA, strlen(ipl->cmdline) + 1);
>> +            size_t cmdline_size = strlen(ipl->cmdline) + 1;
>> +            char *parm_area = rom_ptr(KERN_PARM_AREA, cmdline_size);
>> +
>>               ipl->start_addr = KERN_IMAGE_START;
>>               /* Overwrite parameters in the kernel image, which are "rom" */
>>               if (parm_area) {
>> +                if (cmdline_size > KERN_PARM_AREA_SIZE) {
>> +                    error_setg(errp,
>> +                               "kernel command line exceeds maximum size: %lu > %lu",
>
> I think the first %lu should be %zd instead?

Yep, makes sense - thanks!

>
> Apart from that, the patch looks fine to me... so if you agree, I can fix 
> that up when picking up the patch.

Thanks.

>
>   Thomas
>
>
>> +                               cmdline_size, KERN_PARM_AREA_SIZE);
>> +                    return;
>> +                }
>> +
>>                   strcpy(parm_area, ipl->cmdline);
>>               }
>>           } else {
>> 
>
-- 
Kind regards / Beste Grüße
   Marc Hartmayer

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