vhost: Fix the crash caused by accessing the released memory

The rte_vhost_driver_unregister() vhost_user_read_cb()
vhost_user_client_reconnect() can be called at the same time by 3 threads.
when memory of vsocket is freed in rte_vhost_driver_unregister(),
then vhost_user_read_cb() maybe add vsocket to reconn_list,
the invalid memory of vsocket is accessed in vhost_user_client_reconnect().

The core trace is:
Program terminated with signal 11, Segmentation fault.
The fix is to perform a delete operation again after releasing the memory

Signed-off-by: zhaoxinxin <15957197901@163.com>
---
 lib/vhost/socket.c | 2 ++
 1 file changed, 2 insertions(+)
  

Hi,

On 6/19/24 14:27, zhaoxinxin wrote:
> The rte_vhost_driver_unregister() vhost_user_read_cb()
> vhost_user_client_reconnect() can be called at the same time by 3 threads.
> when memory of vsocket is freed in rte_vhost_driver_unregister(),
> then vhost_user_read_cb() maybe add vsocket to reconn_list,
> the invalid memory of vsocket is accessed in vhost_user_client_reconnect().

It is not clear to me why 3 threads are calling
rte_vhost_driver_unregister() at the same time, isn't it an application
issue?

> The core trace is:
> Program terminated with signal 11, Segmentation fault.
> The fix is to perform a delete operation again after releasing the memory
>

We need a Fixes tag and Cc stable@dpdk.org so that it is backported.

> Signed-off-by: zhaoxinxin <15957197901@163.com>

The format is Firstname Lastname <email>


> ---
>   lib/vhost/socket.c | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/lib/vhost/socket.c b/lib/vhost/socket.c
> index a75728a2e4..01946096c4 100644
> --- a/lib/vhost/socket.c
> +++ b/lib/vhost/socket.c
> @@ -1121,6 +1121,8 @@ rte_vhost_driver_unregister(const char *path)
>   		if (vsocket->is_server) {
>   			close(vsocket->socket_fd);
>   			unlink(path);
> +		} else if (vsocket->reconnect) {
> +			vhost_user_remove_reconnect(vsocket);
>   		}
>   
>   		pthread_mutex_destroy(&vsocket->conn_mutex);
  

Hi Maxime,

The scenario where I encountered coredump was ovs-dpdk，

similar to patch: https://github.com/DPDK/dpdk/commit/52d874dc67055a943867456d3e5c730168bfba18.

Only one thread called rte_vhost_driver_unregister(), but at the same time, 

two other threads called vhost_user_read_cb() and vhost_user_client_reconnect() respectively.




The specific reasons for coredump are as follows：

vhostuser port is created as client.

Thread 1 calls rte_vhost_driver_unregister() to remove the vsocket of reconn from the reconn list.

then “vhost-events” thread calls vhost_user_read_cb() to add the vsocket of reconn back to the reconn list.
At this time, after thread 1 releases the vsocket memory, the socket of vhostuser reconnects successfully, 
"vhost_reconn" thread will access the released memory.
Therefore, The fix is to perform a delete operation again after releasing the memory.




>We need a Fixes tag and Cc stable@dpdk.org so that it is backported.
>The format is Firstname Lastname <email>
I will modify and resubmit the patch, thank you.






At 2024-06-24 17:20:00, "Maxime Coquelin" <maxime.coquelin@redhat.com> wrote: >Hi, > >On 6/19/24 14:27, zhaoxinxin wrote: >> The rte_vhost_driver_unregister() vhost_user_read_cb() >> vhost_user_client_reconnect() can be called at the same time by 3 threads. >> when memory of vsocket is freed in rte_vhost_driver_unregister(), >> then vhost_user_read_cb() maybe add vsocket to reconn_list, >> the invalid memory of vsocket is accessed in vhost_user_client_reconnect(). > >It is not clear to me why 3 threads are calling >rte_vhost_driver_unregister() at the same time, isn't it an application >issue? > >> The core trace is: >> Program terminated with signal 11, Segmentation fault. >> The fix is to perform a delete operation again after releasing the memory >> > >We need a Fixes tag and Cc stable@dpdk.org so that it is backported. > >> Signed-off-by: zhaoxinxin <15957197901@163.com> > >The format is Firstname Lastname <email> > > >> --- >> lib/vhost/socket.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/lib/vhost/socket.c b/lib/vhost/socket.c >> index a75728a2e4..01946096c4 100644 >> --- a/lib/vhost/socket.c >> +++ b/lib/vhost/socket.c >> @@ -1121,6 +1121,8 @@ rte_vhost_driver_unregister(const char *path) >> if (vsocket->is_server) { >> close(vsocket->socket_fd); >> unlink(path); >> + } else if (vsocket->reconnect) { >> + vhost_user_remove_reconnect(vsocket); >> } >> >> pthread_mutex_destroy(&vsocket->conn_mutex);