Re: [Qemu-devel] [PATCH] migration: Replace strncpy() by g_strlcpy()

[David Hildenbrand <david@redhat.com>]

On 20.08.2018 15:23, Paolo Bonzini wrote:
> On 18/08/2018 04:56, Philippe Mathieu-Daudé wrote:
>> Fedora 29 comes with GCC 8.1 which added the 'stringop-truncation' checks.
>>
>> Replace the strncpy() calls by g_strlcpy() to avoid the following warning:
>>
>>   migration/global_state.c: In function 'global_state_store_running':
>>   migration/global_state.c:45:5: error: 'strncpy' specified bound 100 equals destination size [-Werror=stringop-truncation]
>>        strncpy((char *)global_state.runstate,
>>        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>               state, sizeof(global_state.runstate));
>>               ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> Reported-by: Howard Spoelstra <hsp.cat7@gmail.com>
>> Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
>> ---
>> See http://lists.nongnu.org/archive/html/qemu-devel/2018-07/msg03723.html
>>
>>  migration/global_state.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/migration/global_state.c b/migration/global_state.c
>> index 8e8ab5c51e..d5df502cd5 100644
>> --- a/migration/global_state.c
>> +++ b/migration/global_state.c
>> @@ -42,7 +42,7 @@ int global_state_store(void)
>>  void global_state_store_running(void)
>>  {
>>      const char *state = RunState_str(RUN_STATE_RUNNING);
>> -    strncpy((char *)global_state.runstate,
>> +    g_strlcpy((char *)global_state.runstate,
>>             state, sizeof(global_state.runstate));
>>  }
>>  
>>
> 
> This is wrong because strlcpy doesn't zero the rest of

Two RB-s and it is still wrong implies that string operations are still
the root of all evil. :)

> global_state.runstate, so you could end up with something like
> "running\0ate\0\0..." in global_state.runstate However, the same mistake
> is already present in vl.c's runstate_store.
> 
> Juan, David, what to do?  strncpy is easy to misuse, but we do have
> cases where it's correct and it should tingle the reviewers' spidey
> senses...  I wouldn't mind disabling the warning, and using strncpy in
> runstate_store, because in practice it's already reported by Coverity
> and it can be shut up there.

Maybe really set it to zero (memset) before using the g_strlcpy? I am
not a fan of disabling warnings, but if you think this is
easier/cleaner, let's go for that.

> 
> Thanks,
> 
> Paolo
> 


-- 

Thanks,

David / dhildenb