Re: [RHEL7 qemu-kvm PATCH 2/3] s390x: Fix vm name copy length

[Thomas Huth <thuth@redhat.com>]

On 11/01/2021 13.10, Philippe Mathieu-Daudé wrote:
> Hi Miroslav,
> 
> On 1/11/21 12:30 PM, mrezanin@redhat.com wrote:
>> From: Miroslav Rezanina <mrezanin@redhat.com>
>>
>> There are two cases when vm name is copied but closing \0 can be lost
>> in case name is too long (>=256 characters).
>>
>> Updating length to copy so there is space for closing \0.
>>
>> Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
>> ---
>>   target/s390x/kvm.c         | 2 +-
>>   target/s390x/misc_helper.c | 4 +++-
>>   2 files changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
>> index b8385e6b95..2313b5727e 100644
>> --- a/target/s390x/kvm.c
>> +++ b/target/s390x/kvm.c
>> @@ -1918,7 +1918,7 @@ static void insert_stsi_3_2_2(S390CPU *cpu, __u64 addr, uint8_t ar)
>>        */
>>       if (qemu_name) {
>>           strncpy((char *)sysib.ext_names[0], qemu_name,
>> -                sizeof(sysib.ext_names[0]));
>> +                sizeof(sysib.ext_names[0]) - 1);
>>       } else {
>>           strcpy((char *)sysib.ext_names[0], "KVMguest");
>>       }
> 
> What about using strpadcpy() instead?

Yes, strpadcpy is the better way here - this field has to be padded with 
zeroes, so doing "- 1" is wrong here.

  Thomas