Commit e4d221b4 authored Dec 09, 2020 by Andrea Parri (Microsoft) Committed by Wei Liu Feb 05, 2021

Drivers: hv: vmbus: Resolve race condition in vmbus_onoffer_rescind()

An erroneous or malicious host could send multiple rescind messages for
a same channel. In vmbus_onoffer_rescind(), the guest maps the channel
ID to obtain a pointer to the channel object and it eventually releases
such object and associated data. The host could time rescind messages
and lead to an use-after-free. Add a new flag to the channel structure
to make sure that only one instance of vmbus_onoffer_rescind() can get
the reference to the channel object.

Reported-by: Juan Vazquez <juvazq@microsoft.com>
Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20201209070827.29335-6-parri.andrea@gmail.com

Signed-off-by: Wei Liu <wei.liu@kernel.org>

parent e3fa4b74

drivers/hv/channel_mgmt.c

+12 −0

Original line number	Diff line number	Diff line
		@@ -1063,6 +1063,18 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr)

		mutex_lock(&vmbus_connection.channel_mutex);
		channel = relid2channel(rescind->child_relid);
		if (channel != NULL) {
		/*
		* Guarantee that no other instance of vmbus_onoffer_rescind()
		* has got a reference to the channel object. Synchronize on
		* &vmbus_connection.channel_mutex.
		*/
		if (channel->rescind_ref) {
		mutex_unlock(&vmbus_connection.channel_mutex);
		return;
		}
		channel->rescind_ref = true;
		}
		mutex_unlock(&vmbus_connection.channel_mutex);

		if (channel == NULL) {

+1 −0

Original line number	Diff line number	Diff line
		@@ -809,6 +809,7 @@ struct vmbus_channel {
		u8 monitor_bit;

		bool rescind; /* got rescind msg */
		bool rescind_ref; /* got rescind msg, got channel reference */
		struct completion rescind_event;

		u32 ringbuffer_gpadlhandle;