From: Andrea Parri (Microsoft) parri.andrea@gmail.com
[ Upstream commit e3fa4b747f085d2cda09bba0533b86fa76038635 ]
When channel->device_obj is non-NULL, vmbus_onoffer_rescind() could invoke put_device(), that will eventually release the device and free the channel object (cf. vmbus_device_release()). However, a pointer to the object is dereferenced again later to load the primary_channel. The use-after-free can be avoided by noticing that this load/check is redundant if device_obj is non-NULL: primary_channel must be NULL if device_obj is non-NULL, cf. vmbus_add_channel_work().
Fixes: 54a66265d6754b ("Drivers: hv: vmbus: Fix rescind handling") 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/20201209070827.29335-5-parri.andrea@gmail.com Signed-off-by: Wei Liu wei.liu@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/hv/channel_mgmt.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c index 1d44bb635bb84..6be9f56cb6270 100644 --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c @@ -1102,8 +1102,7 @@ static void vmbus_onoffer_rescind(struct vmbus_channel_message_header *hdr) vmbus_device_unregister(channel->device_obj); put_device(dev); } - } - if (channel->primary_channel != NULL) { + } else if (channel->primary_channel != NULL) { /* * Sub-channel is being rescinded. Following is the channel * close sequence when initiated from the driveri (refer to