[Spice-devel] [PATCH spice-server 1/8] red_channel: prevent adding and pushing pipe items after a channel_client has diconnected

[Yonit Halperin]

Fixes: leaks of pipe items & "red_client_destroy: assertion `rcc->send_data.size == 0'"

red_channel_disconnect clears the pipe. It is called only once. After,
it was called, not items should be added to the pipe.

An example of when this assert can occur:
on_new_cursor_channel (red_worker.c), pushes 2 pipe items.
When it pushes the first pipe item, if the client has disconnected,
it can hit a socket error, and then, red_channel_client_disconnect is called.
The second call to adding a pipe item, will add the item to
the pipe. red_channel_client_pipe_add_type also calls
red_channel_client_push, which will update the send_data.size.
Then, the push will also hit a socket error, but red_channel_client_disconnect
won't clear the pending pipe item again, since it was already called.
When red_client_destory is called, we hit assertion `rcc->send_data.size
== 0'.
Note that if a pipe item is added to the pipe after
red_channel_client_disconnect was called, but without pushing it,
we should hit "spice_assert(rcc->pipe_size == 0)".
---
 server/red_channel.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/server/red_channel.c b/server/red_channel.c
index 31c991b..a35da9b 100644
--- a/server/red_channel.c
+++ b/server/red_channel.c
@@ -1524,9 +1524,23 @@ void red_channel_pipe_item_init(RedChannel *channel, PipeItem *item, int type)
     item->type = type;
 }
 
-void red_channel_client_pipe_add(RedChannelClient *rcc, PipeItem *item)
+static inline int validate_pipe_add(RedChannelClient *rcc, PipeItem *item)
 {
     spice_assert(rcc && item);
+    if (SPICE_UNLIKELY(!red_channel_client_is_connected(rcc))) {
+        spice_debug("rcc is disconnected %p", rcc);
+        red_channel_client_release_item(rcc, item, FALSE);
+        return FALSE;
+    }
+    return TRUE;
+}
+
+void red_channel_client_pipe_add(RedChannelClient *rcc, PipeItem *item)
+{
+
+    if (!validate_pipe_add(rcc, item)) {
+        return;
+    }
     rcc->pipe_size++;
     ring_add(&rcc->pipe, &item->link);
 }
@@ -1540,10 +1554,10 @@ void red_channel_client_pipe_add_push(RedChannelClient *rcc, PipeItem *item)
 void red_channel_client_pipe_add_after(RedChannelClient *rcc,
                                        PipeItem *item, PipeItem *pos)
 {
-    spice_assert(rcc);
     spice_assert(pos);
-    spice_assert(item);
-
+    if (!validate_pipe_add(rcc, item)) {
+        return;
+    }
     rcc->pipe_size++;
     ring_add_after(&item->link, &pos->link);
 }
@@ -1557,14 +1571,18 @@ int red_channel_client_pipe_item_is_linked(RedChannelClient *rcc,
 void red_channel_client_pipe_add_tail_no_push(RedChannelClient *rcc,
                                               PipeItem *item)
 {
-    spice_assert(rcc);
+    if (!validate_pipe_add(rcc, item)) {
+        return;
+    }
     rcc->pipe_size++;
     ring_add_before(&item->link, &rcc->pipe);
 }
 
 void red_channel_client_pipe_add_tail(RedChannelClient *rcc, PipeItem *item)
 {
-    spice_assert(rcc);
+    if (!validate_pipe_add(rcc, item)) {
+        return;
+    }
     rcc->pipe_size++;
     ring_add_before(&item->link, &rcc->pipe);
     red_channel_client_push(rcc);
-- 
1.8.1.4