[PATCH] vhost: Fix the crash caused by accessing the released memory

[15957197901]

Hello Maxime Coquelin，




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.



I have resubmitted the patch, please review it again.

https://patches.dpdk.org/project/dpdk/patch/20240625093149.63247-1-15957197901@163.com/







At 2024-06-24 17:20:00, "Maxime Coquelin" <maxime.coquelin at 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 at dpdk.org so that it is backported.
>
>> Signed-off-by: zhaoxinxin <15957197901 at 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);
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