On Wed, Feb 24, 2021 at 07:50:09AM -0500, Sasha Levin wrote:
From: "Andrea Parri (Microsoft)" parri.andrea@gmail.com
[ Upstream commit e4d221b42354b2e2ddb9187a806afb651eee2cda ]
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 Signed-off-by: Sasha Levin sashal@kernel.org
Sasha - This patch is one of a group of patches where a Linux guest running on Hyper-V will start assuming that hypervisor behavior might be malicious, and guards against such behavior. Because this is a new assumption, these patches are more properly treated as new functionality rather than as bug fixes. So I would propose that we *not* bring such patches back to stable branches.
Thanks, Andrea
drivers/hv/channel_mgmt.c | 12 ++++++++++++ include/linux/hyperv.h | 1 + 2 files changed, 13 insertions(+)
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c index 1d44bb635bb84..a9f58840f85dc 100644 --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c @@ -1049,6 +1049,18 @@ 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) { diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index 5ddb479c4d4cb..ef3573e99d989 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -803,6 +803,7 @@ 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; -- 2.27.0