[virt-tools-list] [PATCH v4] remote-viewer: fix free on dangling pointer

[Eduardo Lima (Etrunko)]

On 10/3/19 7:12 AM, Victor Toso wrote:
> From: Victor Toso <me at victortoso.com>
> 
> On remote_viewer_session_connected() we are passing a dup of URI of
> connection and freeing it afterwards. Problem is, we don't disconnect
> from listening "session-connected" and on an eventual second emission
> of this signal, remote-viewer crashes as seen in the backtrace below.
> 
> This can happen over switch-host migration message from
> SpiceMainChannel.
> 
> A fix trying to use VirtViewerApp URI avoid the crash but introduces
> regression while running remote-viewer with ovirt so, keeping the
> changes to a minimum to avoid it, just use g_intern_string() for now.
> 
> Found it while improving migrate.py from spice/tests (server):
>   | Invalid free() / delete / delete[] / realloc()
>   |    at 0x4839A0C: free (vg_replace_malloc.c:540)
>   |    by 0x56EBD8C: g_free (in /usr/lib64/libglib-2.0.so.0.6000.6)
>   |    by 0x11DED0: remote_viewer_session_connected (remote-viewer.c:658)
>   |    by 0x564D741: g_closure_invoke (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x56614F3: ??? (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x566A34D: g_signal_emit_valist (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x566AF68: g_signal_emit_by_name (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x135E5D: virt_viewer_session_spice_main_channel_event (virt-viewer-session-spice.c:699)
>   |    by 0x564D741: g_closure_invoke (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x56614F3: ??? (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x566A34D: g_signal_emit_valist (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x53149E3: emit_main_context (gio-coroutine.c:198)
>   |  Address 0x18f1ecc0 is 0 bytes inside a block of size 23 free'd
>   |    at 0x4839A0C: free (vg_replace_malloc.c:540)
>   |    by 0x56EBD8C: g_free (in /usr/lib64/libglib-2.0.so.0.6000.6)
>   |    by 0x11DED0: remote_viewer_session_connected (remote-viewer.c:658)
>   |    by 0x564D741: g_closure_invoke (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x56614F3: ??? (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x566A34D: g_signal_emit_valist (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x566AF68: g_signal_emit_by_name (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x135E5D: virt_viewer_session_spice_main_channel_event (virt-viewer-session-spice.c:699)
>   |    by 0x564D741: g_closure_invoke (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x56614F3: ??? (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x566A34D: g_signal_emit_valist (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x53149E3: emit_main_context (gio-coroutine.c:198)
>   |  Block was alloc'd at
>   |    at 0x483880B: malloc (vg_replace_malloc.c:309)
>   |    by 0x56EBC98: g_malloc (in /usr/lib64/libglib-2.0.so.0.6000.6)
>   |    by 0x5705C43: g_strdup (in /usr/lib64/libglib-2.0.so.0.6000.6)
>   |    by 0x11EB80: remote_viewer_initial_connect (remote-viewer.c:696)
>   |    by 0x11EB80: remote_viewer_start (remote-viewer.c:790)
>   |    by 0x1250D3: virt_viewer_app_start (virt-viewer-app.c:1727)
>   |    by 0x127108: virt_viewer_app_on_application_startup (virt-viewer-app.c:1870)
>   |    by 0x564D741: g_closure_invoke (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x5661638: ??? (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x566A34D: g_signal_emit_valist (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x566A972: g_signal_emit (in /usr/lib64/libgobject-2.0.so.0.6000.6)
>   |    by 0x553ECA1: g_application_register (in /usr/lib64/libgio-2.0.so.0.6000.6)
>   |    by 0x553F41D: g_application_run (in /usr/lib64/libgio-2.0.so.0.6000.6)
> 
> Signed-off-by: Victor Toso <victortoso at redhat.com>
> ---
>   src/remote-viewer.c | 10 +++-------
>   1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/src/remote-viewer.c b/src/remote-viewer.c
> index 8938ef9..8eaa72e 100644
> --- a/src/remote-viewer.c
> +++ b/src/remote-viewer.c
> @@ -645,17 +645,13 @@ remote_viewer_recent_add(gchar *uri, const gchar *mime_type)
>   
>   static void
>   remote_viewer_session_connected(VirtViewerSession *session,
> -                                gchar *guri)
> +                                const gchar *guri)
>   {
>       gchar *uri = virt_viewer_session_get_uri(session);
>       const gchar *mime = virt_viewer_session_mime_type(session);
>   
> -    if (uri == NULL)
> -        uri = g_strdup(guri);
> -
> -    remote_viewer_recent_add(uri, mime);
> +    remote_viewer_recent_add(uri != NULL ? uri : (char *) guri, mime);

Acked-by: Eduardo Lima (Etrunko) <etrunko at redhat.com>

IMO, removing the "!= NULL" test would make it easier to read, but it is 
just my preference.

>       g_free(uri);
> -    g_free(guri);
>   }
>   
>   static gchar *
> @@ -694,7 +690,7 @@ remote_viewer_initial_connect(RemoteViewer *self, const gchar *type, const gchar
>       }
>   
>       g_signal_connect(virt_viewer_app_get_session(app), "session-connected",
> -                     G_CALLBACK(remote_viewer_session_connected), g_strdup(guri));
> +                     G_CALLBACK(remote_viewer_session_connected), (gpointer) g_intern_string(guri));
>   
>       virt_viewer_session_set_file(virt_viewer_app_get_session(app), vvfile);
>   #ifdef HAVE_OVIRT
> 


-- 
Eduardo de Barros Lima (Etrunko)
Software Engineer - Red Hat
etrunko at redhat.com