diff options
| author | Dexuan Cui <decui@microsoft.com> | 2019-07-31 04:25:45 +0300 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2019-08-03 03:26:27 +0300 |
| commit | 685703b497bacea8765bb409d6b73455b73c540e (patch) | |
| tree | 0b1318ea44c69b0e5e612f4e91c37d2bf9189780 | |
| parent | 224c04973db1125fcebefffd86115f99f50f8277 (diff) | |
| download | linux-685703b497bacea8765bb409d6b73455b73c540e.tar.xz | |
hv_sock: Fix hang when a connection is closed
There is a race condition for an established connection that is being closed
by the guest: the refcnt is 4 at the end of hvs_release() (Note: here the
'remove_sock' is false):
1 for the initial value;
1 for the sk being in the bound list;
1 for the sk being in the connected list;
1 for the delayed close_work.
After hvs_release() finishes, __vsock_release() -> sock_put(sk) *may*
decrease the refcnt to 3.
Concurrently, hvs_close_connection() runs in another thread:
calls vsock_remove_sock() to decrease the refcnt by 2;
call sock_put() to decrease the refcnt to 0, and free the sk;
next, the "release_sock(sk)" may hang due to use-after-free.
In the above, after hvs_release() finishes, if hvs_close_connection() runs
faster than "__vsock_release() -> sock_put(sk)", then there is not any issue,
because at the beginning of hvs_close_connection(), the refcnt is still 4.
The issue can be resolved if an extra reference is taken when the
connection is established.
Fixes: a9eeb998c28d ("hv_sock: Add support for delayed close")
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Sunil Muthuswamy <sunilmut@microsoft.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
| -rw-r--r-- | net/vmw_vsock/hyperv_transport.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c index f2084e3f7aa4..9d864ebeb7b3 100644 --- a/net/vmw_vsock/hyperv_transport.c +++ b/net/vmw_vsock/hyperv_transport.c @@ -312,6 +312,11 @@ static void hvs_close_connection(struct vmbus_channel *chan) lock_sock(sk); hvs_do_close_lock_held(vsock_sk(sk), true); release_sock(sk); + + /* Release the refcnt for the channel that's opened in + * hvs_open_connection(). + */ + sock_put(sk); } static void hvs_open_connection(struct vmbus_channel *chan) @@ -407,6 +412,9 @@ static void hvs_open_connection(struct vmbus_channel *chan) } set_per_channel_state(chan, conn_from_host ? new : sk); + + /* This reference will be dropped by hvs_close_connection(). */ + sock_hold(conn_from_host ? new : sk); vmbus_set_chn_rescind_callback(chan, hvs_close_connection); /* Set the pending send size to max packet size to always get |