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authorDexuan Cui <decui@microsoft.com>2019-07-31 04:25:45 +0300
committerDavid S. Miller <davem@davemloft.net>2019-08-03 03:26:27 +0300
commit685703b497bacea8765bb409d6b73455b73c540e (patch)
tree0b1318ea44c69b0e5e612f4e91c37d2bf9189780
parent224c04973db1125fcebefffd86115f99f50f8277 (diff)
downloadlinux-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.c8
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