[Spice-devel] [PATCH v2] Handle flow control without crashing for agent

[Frediano Ziglio]

RedCharDevice used for the agent has flow control enabled.
This make possible for red_char_device_write_buffer_get to return NULL.
Handle such situation without crashing avoiding NULL dereference.

This fixes https://bugs.freedesktop.org/show_bug.cgi?id=95416.

Signed-off-by: Frediano Ziglio <fziglio at redhat.com>
---
 server/reds.c | 5 +++++
 1 file changed, 5 insertions(+)

Changes from v1:
- put inline comment to explain the reason of the check.

Victor (bug reporter) tested this patch successfully.

diff --git a/server/reds.c b/server/reds.c
index e4d806c..f8cfdfb 100644
--- a/server/reds.c
+++ b/server/reds.c
@@ -1120,6 +1120,11 @@ uint8_t *reds_get_agent_data_buffer(RedsState *reds, MainChannelClient *mcc, siz
     dev->priv->recv_from_client_buf = red_char_device_write_buffer_get(RED_CHAR_DEVICE(dev),
                                                                        client,
                                                                        size + sizeof(VDIChunkHeader));
+    /* check if buffer was allocated, as flow control is enabled for
+     * this device this is a normal condition */
+    if (!dev->priv->recv_from_client_buf) {
+        return NULL;
+    }
     dev->priv->recv_from_client_buf_pushed = FALSE;
     return dev->priv->recv_from_client_buf->buf + sizeof(VDIChunkHeader);
 }
-- 
2.7.4