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

[Olivier Matz <olivier.matz@6wind.com>]

On Thu, Apr 15, 2021 at 08:51:27AM -0400, Aaron Conole wrote:
> 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?

Good point, we can indeed add something in the API documentation. To
detect that the private area is not big enough in rte_pktmbuf_init(),
unfortunatly the function has no return code, but for now we can add at
least an RTE_ASSERT() (only active when -DRTE_ENABLE_ASSERT is passed),
as it's already done for other checks.

I can do a new version of the patch. Wenwu, is it ok for you?

In a second step, we can think about changing the API of all mempool
callbacks and their wrappers to add a return code.


> > 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
>