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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>
This commit is contained in:
Andrea Parri (Microsoft) 2020-12-09 08:08:26 +01:00 committed by Wei Liu
parent e3fa4b747f
commit e4d221b423
2 changed files with 13 additions and 0 deletions
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12
drivers/hv/channel_mgmt.c
View File

@ -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
include/linux/hyperv.h
View File

@ -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;