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server/red_channel: fix possible access to released channel clients

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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.
This commit is contained in:
Yonit Halperin 2012-05-31 09:39:14 +03:00
parent d691602784
commit 2d2121a170
2 changed files with 104 additions and 20 deletions
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119
server/red_channel.c
View File

@ -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;

5
server/red_channel.h
View File

@ -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;