Re: [dpdk-dev] [PATCH v2] ring: fix use after free in ring release

[Konstantin Ananyev <konstantin.v.ananyev@yandex.ru>]

> 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: stable@dpdk.org
> 
> Suggested-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
> Signed-off-by: Yunjian Wang <wangyunjian@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.
Apart from that, LGTM.
Acked-by: Konstantin Ananyev <konstantin.v.ananyev@yandex.ru>

>  	rte_mcfg_tailq_write_unlock();
>  
>  	rte_free(te);
> -- 
> 2.33.0