[External] Re: [PATCH v2] mempool: fix rte_mempool_avail_count may segment fault when used in multiprocess

[Stephen Hemminger]

On Tue, 29 Nov 2022 17:57:05 +0800
Fengnan Chang <changfengnan at bytedance.com> wrote:

> Olivier Matz <olivier.matz at 6wind.com> 于2022年11月22日周二 23:25写道：
> >
> > Hi,
> >
> > On Tue, Nov 15, 2022 at 08:35:02PM +0800, Fengnan Chang wrote:  
> > > rte_mempool_create put tailq entry into rte_mempool_tailq list before
> > > populate, and pool_data set when populate. So in multi process, if
> > > process A create mempool, and process B can get mempool through
> > > rte_mempool_lookup before pool_data set, if B call rte_mempool_avail_count,
> > > it will cause segment fault.
> > >
> > > Fix this by put tailq entry into rte_mempool_tailq after populate.
> > >
> > > Signed-off-by: Fengnan Chang <changfengnan at bytedance.com>

Why not just handle this in rte_mempool_avail_count?  It would be much simpler there.


diff --git a/lib/mempool/rte_mempool.c b/lib/mempool/rte_mempool.c
index 4d337fca8dcd..14855e21801f 100644
--- a/lib/mempool/rte_mempool.c
+++ b/lib/mempool/rte_mempool.c
@@ -1006,6 +1006,10 @@ rte_mempool_avail_count(const struct rte_mempool *mp)
        unsigned count;
        unsigned lcore_id;
 
+       /* Handle race where pool created but ops not allocated yet */
+       if (!(mp->flags & RTE_MEMPOOL_F_POOL_CREATED))
+               return 0;
+
        count = rte_mempool_ops_get_count(mp);
 
        if (mp->cache_size == 0)