Re: [dpdk-dev] [PATCH v7] vhost: fix crash on port deletion

["Xia, Chenbo" <chenbo.xia@intel.com>]

Hi,

> -----Original Message-----
> From: Gaoxiang Liu <gaoxiangliu0@163.com>
> Sent: Thursday, September 2, 2021 11:46 PM
> To: maxime.coquelin@redhat.com; Xia, Chenbo <chenbo.xia@intel.com>
> Cc: dev@dpdk.org; liugaoxiang@huawei.com; Gaoxiang Liu <gaoxiangliu0@163.com>
> Subject: [PATCH v7] vhost: fix crash on port deletion
> 
> The rte_vhost_driver_unregister() and vhost_user_read_cb()
> can be called at the same time by 2 threads.
> when memory of vsocket is freed in rte_vhost_driver_unregister(),
> the invalid memory of vsocket is accessed in vhost_user_read_cb().
> It's a bug of both mode for vhost as server or client.
> 
> E.g., vhostuser port is created as server.
> Thread1 calls rte_vhost_driver_unregister().
> Before the listen fd is deleted from poll waiting fds,
> "vhost-events" thread then calls vhost_user_server_new_connection(),
> then a new conn fd is added in fdset when trying to reconnect.
> "vhost-events" thread then calls vhost_user_read_cb() and
> accesses invalid memory of socket while thread1 frees the memory of
> vsocket.
> 
> E.g., vhostuser port is created as client.
> Thread1 calls rte_vhost_driver_unregister().
> Before vsocket of reconn is deleted from reconn list,
> "vhost_reconn" thread then calls vhost_user_add_connection()
> then a new conn fd is added in fdset when trying to reconnect.
> "vhost-events" thread then calls vhost_user_read_cb() and
> accesses invalid memory of socket while thread1 frees the memory of
> vsocket.
> 
> The fix is to move the "fdset_try_del" in front of free memory of conn,
> then avoid the race condition.
> 
> The core trace is:
> Program terminated with signal 11, Segmentation fault.
> 
> Fixes: 52d874dc6705 ("vhost: fix crash on closing in client mode")

Please check comment/reply in v6. And a suggestion:

Wait for comment/problem solved in old version before new version.
It can save everyone's effort of tracking all versions.