[sheepdog] [PATCH 2/2] fix array index error in function add_new_participant
Ruoyu
liangry at ucweb.com
Tue Aug 12 03:25:49 CEST 2014
On 2014年08月11日 21:45, Hitoshi Mitake wrote:
> At Mon, 11 Aug 2014 18:11:44 +0800,
> Ruoyu wrote:
>> Nothing wrong with fixing it, alhough I don't know exactly
>> what will be happened if not patching it.
>>
>> Signed-off-by: Ruoyu <liangry at ucweb.com>
>> ---
>> sheep/vdi.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/sheep/vdi.c b/sheep/vdi.c
>> index 05cae7b..77dc253 100644
>> --- a/sheep/vdi.c
>> +++ b/sheep/vdi.c
>> @@ -372,11 +372,12 @@ static bool add_new_participant(struct vdi_state_entry *entry,
>> return true;
>> }
>>
>> - idx = entry->nr_participants++;
>> + idx = entry->nr_participants;
>> memcpy(&entry->participants[idx], owner, sizeof(*owner));
>> entry->participants_state[idx] =
>> is_modified(entry) ?
>> SHARED_LOCK_STATE_INVALIDATED : SHARED_LOCK_STATE_SHARED;
>> + entry->nr_participants++;
> I think this patch doesn't change the function. Does this fixes a bug?
It fixes a logical error. Otherwise, there should be a hole in the array
if new participant is added.
For example,
// supposed entry->nr_participants is 2;
idx = entry->nr_participants++;
// idx is 3 now;
memcpy(&entry->participants[idx], owner, sizeof(*owner));
entry->participants_state[idx] =
is_modified(entry) ?
SHARED_LOCK_STATE_INVALIDATED : SHARED_LOCK_STATE_SHARED;
// the 4th element is assigned(the 1st is array[0]), but we should modify the 3rd one logically
>
> Thanks,
> Hitoshi
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