> -----Original Message-----
> From: Konstantin Ananyev <konstantin.v.anan...@yandex.ru>
> Sent: Monday, May 1, 2023 7:32 AM
> To: wangyunj...@huawei.com
> Cc: dev@dpdk.org; Honnappa Nagarahalli
> <honnappa.nagaraha...@arm.com>; konstantin.v.anan...@yandex.ru;
> luyi...@huawei.com; sta...@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v2] ring: fix use after free in ring release
>
>
>
> > After the memzone is freed, it is not removed from the 'rte_ring_tailq'.
> > If rte_ring_lookup is called at this time, it will cause a
> > use-after-free problem. This change prevents that from happening.
> >
> > Fixes: 4e32101f9b01 ("ring: support freeing")
> > Cc: sta...@dpdk.org
> >
> > Suggested-by: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>
> > Signed-off-by: Yunjian Wang <wangyunj...@huawei.com>
> > ---
> > v2: update code suggested by Honnappa Nagarahalli
> > ---
> > lib/ring/rte_ring.c | 8 +++-----
> > 1 file changed, 3 insertions(+), 5 deletions(-)
> >
> > diff --git a/lib/ring/rte_ring.c b/lib/ring/rte_ring.c index
> > 8ed455043d..2755323b8a 100644
> > --- a/lib/ring/rte_ring.c
> > +++ b/lib/ring/rte_ring.c
> > @@ -333,11 +333,6 @@ rte_ring_free(struct rte_ring *r)
> > return;
> > }
> >
> > - if (rte_memzone_free(r->memzone) != 0) {
> > - RTE_LOG(ERR, RING, "Cannot free memory\n");
> > - return;
> > - }
> > -
> > ring_list = RTE_TAILQ_CAST(rte_ring_tailq.head, rte_ring_list);
> > rte_mcfg_tailq_write_lock();
> >
> > @@ -354,6 +349,9 @@ rte_ring_free(struct rte_ring *r)
> >
> > TAILQ_REMOVE(ring_list, te, next);
> >
> > + if (rte_memzone_free(r->memzone) != 0)
> > + RTE_LOG(ERR, RING, "Cannot free memory\n");
> > +
>
> I nit: I think it is a bit better to first release the lock and then free the
> memzone.
I think both of our suggestions are contradictory. Any reason why you want to
free outside the locked region?
I thought, since it belongs to the ring being freed, it makes sense to free it
while holding the lock to avoid any race conditions (though, I have not checked
what those are).
> Apart from that, LGTM.
> Acked-by: Konstantin Ananyev <konstantin.v.anan...@yandex.ru>
>
> > rte_mcfg_tailq_write_unlock();
> >
> > rte_free(te);
> > --
> > 2.33.0
>
