From 624d18332e13700b845394b07bbac630adbbdb96 Mon Sep 17 00:00:00 2001 From: "Andrea Parri (Microsoft)" Date: Wed, 9 Dec 2020 08:08:25 +0100 Subject: [PATCH] Drivers: hv: vmbus: Avoid use-after-free in vmbus_onoffer_rescind() [ 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 Signed-off-by: Andrea Parri (Microsoft) Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20201209070827.29335-5-parri.andrea@gmail.com Signed-off-by: Wei Liu Signed-off-by: Sasha Levin --- 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 452307c79e4b9..0b55bc146b292 100644 --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c @@ -1101,8 +1101,7 @@ 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primary_channel != NULL) { /* * Sub-channel is being rescinded.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