From: "Andrea Parri (Microsoft)" <parri.andrea@xxxxxxxxx> [ 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@xxxxxxxxxxxxx> Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@xxxxxxxxx> Reviewed-by: Michael Kelley <mikelley@xxxxxxxxxxxxx> Link: https://lore.kernel.org/r/20201209070827.29335-6-parri.andrea@xxxxxxxxx Signed-off-by: Wei Liu <wei.liu@xxxxxxxxxx> Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> --- 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
