[Spice-devel] [PATCH spice-server 1/2] server/red_channel: fix possible access to released channel clients
Alon Levy
alevy at redhat.com
Thu May 31 00:20:54 PDT 2012
On Thu, May 31, 2012 at 10:04:05AM +0300, Yonit Halperin wrote:
> Added ref count for RedChannel and RedChannelClient.
>
> red_channel.c/red_peer_handle_incoming call to
> handler->cb->handle_message might lead to the release of the channel
> client, and the following call to handler->cb->release_msg_buf will be
> a violation.
>
> This bug can be produced by causing main_channel_handle_parsed
> call red_client_destory, e.g., by some violation in
> reds_on_main_agent_data that will result in a call to reds_disconnect.
ACK both.
> ---
> server/red_channel.c | 119 +++++++++++++++++++++++++++++++++++++++++--------
> server/red_channel.h | 5 ++
> 2 files changed, 104 insertions(+), 20 deletions(-)
>
> diff --git a/server/red_channel.c b/server/red_channel.c
> index 83a9f37..de50047 100644
> --- a/server/red_channel.c
> +++ b/server/red_channel.c
> @@ -43,6 +43,45 @@ static void red_client_remove_channel(RedChannelClient *rcc);
> static RedChannelClient *red_client_get_channel(RedClient *client, int type, int id);
> static void red_channel_client_restore_main_sender(RedChannelClient *rcc);
>
> +/*
> + * Lifetime of RedChannel, RedChannelClient and RedClient:
> + * RedChannel is created and destroyed by the calls to
> + * red_channel_create.* and red_channel_destroy. The RedChannel resources
> + * are deallocated only after red_channel_destroy is called and no RedChannelClient
> + * refers to the channel.
> + * RedChannelClient is created and destroyed by the calls to red_channel_client_create
> + * and red_channel_client_destroy. RedChannelClient resources are deallocated only when
> + * its refs == 0. The reference count of RedChannelClient can be increased by routines
> + * that include calls that might destroy the red_channel_client. For example,
> + * red_peer_handle_incoming calls the handle_message proc of the channel, which
> + * might lead to destroying the client. However, after the call to handle_message,
> + * there is a call to the channel's release_msg_buf proc.
> + *
> + * Once red_channel_client_destroy is called, the RedChannelClient is disconnected and
> + * removed from the RedChannel clients list, but if rcc->refs != 0, it will still hold
> + * a reference to the Channel. The reason for this is that on the one hand RedChannel holds
> + * callbacks that may be still in use by RedChannel, and on the other hand,
> + * when an operation is performed on the list of clients that belongs to the channel,
> + * we don't want to execute it on the "to be destroyed" channel client.
> + *
> + * RedClient is created and destroyed by the calls to red_client_new and red_client_destroy.
> + * When it is destroyed, it also disconnects and destroys all the RedChannelClients that
> + * are associated with it. However, since part of these channel clients may still have
> + * other references, they will not be completely released, until they are dereferenced.
> + *
> + * Note: red_channel_client_destroy is not thread safe, and still it is called from
> + * red_client_destroy (from the client's thread). However, since before this call,
> + * red_client_destroy calls rcc->channel->client_cbs.disconnect(rcc), which is synchronous,
> + * we assume that if the channel is in another thread, it does no longer have references to
> + * this channel client.
> + * If a call to red_channel_client_destroy is made from another location, it must be called
> + * from the channel's thread.
> +*/
> +static void red_channel_ref(RedChannel *channel);
> +static void red_channel_unref(RedChannel *channel);
> +static void red_channel_client_ref(RedChannelClient *rcc);
> +static void red_channel_client_unref(RedChannelClient *rcc);
> +
> static uint32_t full_header_get_msg_size(SpiceDataHeaderOpaque *header)
> {
> return ((SpiceDataHeader *)header->data)->size;
> @@ -245,7 +284,9 @@ static void red_peer_handle_incoming(RedsStream *stream, IncomingHandler *handle
>
> void red_channel_client_receive(RedChannelClient *rcc)
> {
> + red_channel_client_ref(rcc);
> red_peer_handle_incoming(rcc->stream, &rcc->incoming);
> + red_channel_client_unref(rcc);
> }
>
> void red_channel_receive(RedChannel *channel)
> @@ -541,6 +582,7 @@ RedChannelClient *red_channel_client_create(int size, RedChannel *channel, RedCl
> rcc->stream = stream;
> rcc->channel = channel;
> rcc->client = client;
> + rcc->refs = 1;
> rcc->ack_data.messages_window = ~0; // blocks send message (maybe use send_data.blocked +
> // block flags)
> rcc->ack_data.client_generation = ~0;
> @@ -585,6 +627,7 @@ RedChannelClient *red_channel_client_create(int size, RedChannel *channel, RedCl
> rcc->id = channel->clients_num;
> red_channel_add_client(channel, rcc);
> red_client_add_channel(client, rcc);
> + red_channel_ref(channel);
> pthread_mutex_unlock(&client->lock);
> return rcc;
> error:
> @@ -628,6 +671,7 @@ RedChannel *red_channel_create(int size,
> channel = spice_malloc0(size);
> channel->type = type;
> channel->id = id;
> + channel->refs = 1;
> channel->handle_acks = handle_acks;
> memcpy(&channel->channel_cbs, channel_cbs, sizeof(ChannelCbs));
>
> @@ -693,6 +737,7 @@ RedChannel *red_channel_create_dummy(int size, uint32_t type, uint32_t id)
> channel = spice_malloc0(size);
> channel->type = type;
> channel->id = id;
> + channel->refs = 1;
> channel->core = &dummy_core;
> ring_init(&channel->clients);
> client_cbs.connect = red_channel_client_default_connect;
> @@ -790,6 +835,50 @@ void red_channel_set_data(RedChannel *channel, void *data)
> channel->data = data;
> }
>
> +static void red_channel_ref(RedChannel *channel)
> +{
> + channel->refs++;
> +}
> +
> +static void red_channel_unref(RedChannel *channel)
> +{
> + if (!--channel->refs) {
> + if (channel->local_caps.num_common_caps) {
> + free(channel->local_caps.common_caps);
> + }
> +
> + if (channel->local_caps.num_caps) {
> + free(channel->local_caps.caps);
> + }
> +
> + free(channel);
> + }
> +}
> +
> +static void red_channel_client_ref(RedChannelClient *rcc)
> +{
> + rcc->refs++;
> +}
> +
> +static void red_channel_client_unref(RedChannelClient *rcc)
> +{
> + if (!--rcc->refs) {
> + if (rcc->send_data.main.marshaller) {
> + spice_marshaller_destroy(rcc->send_data.main.marshaller);
> + }
> +
> + if (rcc->send_data.urgent.marshaller) {
> + spice_marshaller_destroy(rcc->send_data.urgent.marshaller);
> + }
> +
> + red_channel_client_destroy_remote_caps(rcc);
> + if (rcc->channel) {
> + red_channel_unref(rcc->channel);
> + }
> + free(rcc);
> + }
> +}
> +
> void red_channel_client_destroy(RedChannelClient *rcc)
> {
> rcc->destroying = 1;
> @@ -797,16 +886,7 @@ void red_channel_client_destroy(RedChannelClient *rcc)
> red_channel_client_disconnect(rcc);
> }
> red_client_remove_channel(rcc);
> - if (rcc->send_data.main.marshaller) {
> - spice_marshaller_destroy(rcc->send_data.main.marshaller);
> - }
> -
> - if (rcc->send_data.urgent.marshaller) {
> - spice_marshaller_destroy(rcc->send_data.urgent.marshaller);
> - }
> -
> - red_channel_client_destroy_remote_caps(rcc);
> - free(rcc);
> + red_channel_client_unref(rcc);
> }
>
> void red_channel_destroy(RedChannel *channel)
> @@ -822,15 +902,7 @@ void red_channel_destroy(RedChannel *channel)
> SPICE_CONTAINEROF(link, RedChannelClient, channel_link));
> }
>
> - if (channel->local_caps.num_common_caps) {
> - free(channel->local_caps.common_caps);
> - }
> -
> - if (channel->local_caps.num_caps) {
> - free(channel->local_caps.caps);
> - }
> -
> - free(channel);
> + red_channel_unref(channel);
> }
>
> void red_channel_client_shutdown(RedChannelClient *rcc)
> @@ -845,7 +917,9 @@ void red_channel_client_shutdown(RedChannelClient *rcc)
>
> void red_channel_client_send(RedChannelClient *rcc)
> {
> + red_channel_client_ref(rcc);
> red_peer_handle_outgoing(rcc->stream, &rcc->outgoing);
> + red_channel_client_unref(rcc);
> }
>
> void red_channel_send(RedChannel *channel)
> @@ -886,7 +960,7 @@ void red_channel_client_push(RedChannelClient *rcc)
> } else {
> return;
> }
> -
> + red_channel_client_ref(rcc);
> if (rcc->send_data.blocked) {
> red_channel_client_send(rcc);
> }
> @@ -900,6 +974,7 @@ void red_channel_client_push(RedChannelClient *rcc)
> red_channel_client_send_item(rcc, pipe_item);
> }
> rcc->during_send = FALSE;
> + red_channel_client_unref(rcc);
> }
>
> void red_channel_push(RedChannel *channel)
> @@ -997,12 +1072,14 @@ static void red_channel_client_event(int fd, int event, void *data)
> {
> RedChannelClient *rcc = (RedChannelClient *)data;
>
> + red_channel_client_ref(rcc);
> if (event & SPICE_WATCH_EVENT_READ) {
> red_channel_client_receive(rcc);
> }
> if (event & SPICE_WATCH_EVENT_WRITE) {
> red_channel_client_push(rcc);
> }
> + red_channel_client_unref(rcc);
> }
>
> void red_channel_client_init_send_data(RedChannelClient *rcc, uint16_t msg_type, PipeItem *item)
> @@ -1246,8 +1323,10 @@ RedChannelClient *red_channel_client_create_dummy(int size,
> goto error;
> }
> rcc = spice_malloc0(size);
> + rcc->refs = 1;
> rcc->client = client;
> rcc->channel = channel;
> + red_channel_ref(channel);
> red_channel_client_set_remote_caps(rcc, num_common_caps, common_caps, num_caps, caps);
> if (red_channel_client_test_remote_common_cap(rcc, SPICE_COMMON_CAP_MINI_HEADER)) {
> rcc->incoming.header = mini_header_wrapper;
> diff --git a/server/red_channel.h b/server/red_channel.h
> index 765b74e..e77e484 100644
> --- a/server/red_channel.h
> +++ b/server/red_channel.h
> @@ -225,6 +225,9 @@ struct RedChannelClient {
> RedChannel *channel;
> RedClient *client;
> RedsStream *stream;
> +
> + uint32_t refs;
> +
> struct {
> uint32_t generation;
> uint32_t client_generation;
> @@ -268,6 +271,8 @@ struct RedChannel {
> uint32_t type;
> uint32_t id;
>
> + uint32_t refs;
> +
> RingItem link; // channels link for reds
>
> SpiceCoreInterface *core;
> --
> 1.7.7.6
>
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