Re: [dpdk-dev] [dpdk-stable] [v2] test/mempool: fix heap buffer overflow

[Aaron Conole <aconole@redhat.com>]

Olivier Matz <olivier.matz@6wind.com> writes:

> On Tue, Apr 13, 2021 at 01:52:26PM +0200, Thomas Monjalon wrote:
>> 13/04/2021 22:05, Wenwu Ma:
>> > Amount of allocated memory was not enough for mempool
>> > which cause buffer overflow when access fields of mempool
>> > private structure in the rte_pktmbuf_priv_size function.
>>
>> Was it causing the test to fail?
>> How do you reproduce the overflow?
>
> In the test, right after the rte_mempool_create(), the function
> rte_mempool_obj_iter() is called too initialize the mempool objects with
> the rte_pktmbuf_init() callback function. This callback expects that the
> mempool is a packet pool, i.e. its private area is a struct
> rte_pktmbuf_pool_private structure.
>
> In the current test, the size of the private area is 0, which probably
> causes the function rte_pktmbuf_priv_size() to return an unpredictable
> value, and this value is used as a size in a memset.

Is it possible to have rte_mempool_get_priv() detect that the private
area isn't valid and return a ref to a const static member for this that
will have the correct mbuf_priv_size?  There isn't really documentation
that I can find that describes this corner case with the mempool private
data section.  Actually, it doesn't really say what happens if private
data size is 0, so maybe a documentation update should go with this test
case fix, too?

> This part of the test was added in commit 923ceaeac140 ("test/mempool:
> add unit test cases").
>
> Instead of changing the size of the private area like done in the patch,
> I suggest to use another callback than rte_pktmbuf_init(). After all,
> this is a mempool test, so we should not rely on mbuf features. The
> function my_obj_init() could be used like in other places of the test,
> like this:
>
>   @@ -552,7 +552,7 @@ test_mempool(void)
>   		 GOTO_ERR(ret, err);
>   
>   	 /* test to initialize mempool objects and memory */
>   -        nb_objs = rte_mempool_obj_iter(mp_stack_mempool_iter, rte_pktmbuf_init,
>   +        nb_objs = rte_mempool_obj_iter(mp_stack_mempool_iter, my_obj_init,
>   			 NULL);
>   	 if (nb_objs == 0)
>   		 GOTO_ERR(ret, err);
>
>
> Wenwu, does it solve your issue?
>
>
> Regards,
> Olivier