From 52c7803f9bd4b1f0ac6e2e3e6051415198cc06bd Mon Sep 17 00:00:00 2001 From: Vitaly Kuznetsov Date: Mon, 6 Apr 2020 12:43:26 +0200 Subject: Drivers: hv: check VMBus messages lengths VMBus message handlers (channel_message_table) receive a pointer to 'struct vmbus_channel_message_header' and cast it to a structure of their choice, which is sometimes longer than the header. We, however, don't check that the message is long enough so in case hypervisor screws up we'll be accessing memory beyond what was allocated for temporary buffer. Previously, we used to always allocate and copy 256 bytes from message page to temporary buffer but this is hardly better: in case the message is shorter than we expect we'll be trying to consume garbage as some real data and no memory guarding technique will be able to identify an issue. Introduce 'min_payload_len' to 'struct vmbus_channel_message_table_entry' and check against it in vmbus_on_msg_dpc(). Note, we can't require the exact length as new hypervisor versions may add extra fields to messages, we only check that the message is not shorter than we expect. Signed-off-by: Vitaly Kuznetsov Reviewed-by: Michael Kelley Link: https://lore.kernel.org/r/20200406104326.45361-1-vkuznets@redhat.com Signed-off-by: Wei Liu --- drivers/hv/vmbus_drv.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'drivers/hv/vmbus_drv.c') diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 6e54adb1dd33..3a05e1bc359c 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -1082,6 +1082,12 @@ void vmbus_on_msg_dpc(unsigned long data) if (!entry->message_handler) goto msg_handled; + if (msg->header.payload_size < entry->min_payload_len) { + WARN_ONCE(1, "message too short: msgtype=%d len=%d\n", + hdr->msgtype, msg->header.payload_size); + goto msg_handled; + } + if (entry->handler_type == VMHT_BLOCKING) { ctx = kmalloc(sizeof(*ctx) + msg->header.payload_size, GFP_ATOMIC); -- cgit v1.2.3