Hey, On Tue, Sep 29, 2015 at 11:53:40AM +0200, Christophe Fergeau wrote: > When redirecting a USB webcam over a slow link, it's currently possible > to hit an assertion in spice-server by running cheese (application using > the webcam), killing the client with ctrl+c and then restarting the > client: > qemu-kvm: spicevmc.c:324: spicevmc_red_channel_alloc_msg_rcv_buf: > Assertion `!state->recv_from_client_buf' failed. > > This happens when red_peer_handle_incoming tries to allocate memory for > a message using spicevmc: > handler->msg = handler->cb->alloc_msg_buf(handler->opaque, msg_type, > msg_size); > > red_peer_handle_incoming() is called when there is client data to be > read, and does > - call alloc_msg_buf() to allocate memory for the message > - read the message > - if the read was partial, return early, the main loop will call again > red_peer_handle_incoming() when there is more data available for that > channel > - parse the message > - call release_msg_buf() to free the message > > For channels based on spicevmc (usbredir and port), alloc_msg_buf() > stores message data in SpiceVmcState::recv_from_client_buf and before > allocating new memory, it asserts that it's NULL. This is a great description of message/memory handling in this channels. > > This is what causes this crash in the following scenario: > - SpiceVmc::alloc_msg_buf() is called and allocates memory for a new > message in SpiceVmcState::recv_from_client_buf > - red_peer_handle_incoming() returns early as all the spicevmc message > data hasn't been received yet > - the client gets killed > - the main channel notices the disconnect and calls > main_dispatcher_client_disconnect() which will disconnect all the > channels > - SpiceVmc::on_disconnect is called > - after the new client connects, SpiceVmc::alloc_msg_buf() is called, > notices that SpiceVmcState::recv_from_client_buf is already set, and > asserts() > > This commit makes sure the partial SpiceVmcState::recv_from_client_buf > data is cleared on disconnect so that the assert does not trigger. > > This fixes https://bugzilla.redhat.com/show_bug.cgi?id=1264113 > --- > server/spicevmc.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/server/spicevmc.c b/server/spicevmc.c > index e10f183..80f3aeb 100644 > --- a/server/spicevmc.c > +++ b/server/spicevmc.c > @@ -223,6 +223,11 @@ static void spicevmc_red_channel_client_on_disconnect(RedChannelClient *rcc) > sin = state->chardev_sin; > sif = SPICE_CONTAINEROF(sin->base.sif, SpiceCharDeviceInterface, base); > > + if (state->recv_from_client_buf) { /* partial message which wasn't pushed to device */ > + spice_char_device_write_buffer_release(state->chardev_st, state->recv_from_client_buf); > + state->recv_from_client_buf = NULL; > + } > + > if (state->chardev_st) { > if (spice_char_device_client_exists(state->chardev_st, rcc->client)) { > spice_char_device_client_remove(state->chardev_st, rcc->client); > -- > 2.5.0 That's make sense. Have you tested this on migration as well? IIRC channel is disconnected during migration. cheers, toso _______________________________________________ Spice-devel mailing list Spice-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/spice-devel