<snip>
> >
> > > -----Original Message-----
> > > From: Yunjian Wang <wangyunj...@huawei.com>
> > > Sent: Monday, April 17, 2023 8:12 AM
> > > To: dev@dpdk.org
> > > Cc: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>;
> > > konstantin.v.anan...@yandex.ru; luyi...@huawei.com; Yunjian Wang
> > > <wangyunj...@huawei.com>; sta...@dpdk.org
> > > Subject: [dpdk-dev] [PATCH] ring: fix use after free in ring release
> > >
> > > When using the ring to find out tailq entry, however it had been
> > > freed by rte_memzone_free function. This change prevents that from
> happening.
> > I am unable to follow the problem you are describing.
> > After the memzone for the ring is released, the contents of the
> > memzone are not being used. I understand that the variable 'r' is
> > being used, but that should not cause any issues.
> >
> > >
> > > Fixes: 4e32101f9b01 ("ring: support freeing")
> > > Cc: sta...@dpdk.org
> > >
> > > Signed-off-by: Yunjian Wang <wangyunj...@huawei.com>
> > > ---
> > > lib/ring/rte_ring.c | 11 +++++------
> > > 1 file changed, 5 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/lib/ring/rte_ring.c b/lib/ring/rte_ring.c index
> > > 8ed455043d..17d2d7f8a8 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;
> > > - }
> > Why do we need to free the memzone later?
>
> 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.
Thanks, understood
>
> Thanks,
> Yunjian
> >
> > > -
> > > ring_list = RTE_TAILQ_CAST(rte_ring_tailq.head, rte_ring_list);
> > > rte_mcfg_tailq_write_lock();
> > >
> > > @@ -349,7 +344,7 @@ rte_ring_free(struct rte_ring *r)
> > >
> > > if (te == NULL) {
> > > rte_mcfg_tailq_write_unlock();
> > > - return;
> > > + goto free_memzone;
We do not need this. If 'te == NULL' is true, then the ring was not found or
possibly already freed.
> > > }
> > >
> > > TAILQ_REMOVE(ring_list, te, next); @@ -357,6 +352,10 @@
> > > rte_ring_free(struct rte_ring *r)
We should free the memzone here while holding the lock
> > > rte_mcfg_tailq_write_unlock();
> > >
> > > rte_free(te);
> > > +
> > > +free_memzone:
> > > + if (rte_memzone_free(r->memzone) != 0)
> > > + RTE_LOG(ERR, RING, "Cannot free memory\n");
> > > }
Should be moved up as mentioned above
> > >
> > > /* dump the status of the ring on the console */
> > > --
> > > 2.33.0
