On 2020/8/10 21:48, Martin Wilck wrote:
> Hello Liu,
>
> On Fri, 2020-07-31 at 18:41 +0800, Zhiqiang Liu wrote:
>> In vector_alloc_slot func, if REALLOC fails, it means new slot
>> allocation fails. However, it just update v->allocated and then
>> return the old v->slot without new slot. So, the caller will take
>> the last old slot as the new allocated slot, and use it by calling
>> vector_set_slot func. Finally, the data of last slot is lost.
>>
>> Here, if REALLOC or MALLOC fails, we will return NULL.
>>
>> Signed-off-by: Zhiqiang Liu <liuzhiqiang26@xxxxxxxxxx>
>> Signed-off-by: lixiaokeng <lixiaokeng@xxxxxxxxxx>
>> ---
>> libmultipath/vector.c | 10 ++++++----
>> 1 file changed, 6 insertions(+), 4 deletions(-)
>>
>> diff --git a/libmultipath/vector.c b/libmultipath/vector.c
>> index 501cf4c5..29dc9848 100644
>> --- a/libmultipath/vector.c
>> +++ b/libmultipath/vector.c
>> @@ -49,12 +49,14 @@ vector_alloc_slot(vector v)
>> else
>> new_slot = (void *) MALLOC(sizeof (void *) * v-
>>> allocated);
>>
>> - if (!new_slot)
>> + /* If REALLOC or MALLOC fails, it means new slot allocation
>> fails, so return NULL. */
>> + if (!new_slot) {
>> v->allocated -= VECTOR_DEFAULT_SIZE;
>> - else
>> - v->slot = new_slot;
>> + return NULL;
>> + }
>>
>> - return v->slot;
>> + v->slot = new_slot;
>> + return v->slot[VECTOR_SIZE(v) - 1];
>
> This changes the semantics of the function by returning the last
> element of the vector rather than v->slot. That's dangerous because
> these elements aren't initialized. You might as well return NULL in
> case of success, which would obviously be wrong (actually, new elements
> _should_ be initialized to NULL). As the return value is only ever used
> to check for successful allocation, it might be best to change it into
> a bool, avoiding any ambiguity about its meaning.
>
> If you want to clean up this function (appreciated!), please do it
> right:
>
> - increment v->allocated only after successful allocation,
> - avoid the "if (v->slot)" conditional by just calling realloc(),
> - make sure all newly allocated vector elements are set to NULL,
> - optionally, change return value to bool (see above).
>
> Regards,
> Martin
>
Thanks for your suggestion.
I will rewrite and send the v2 patch as your suggestion.
>
>
> .
>
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