vmci: Prevent the dispatching of uninitialized payloads

Lizhi Xu · gregkh · commit bfb4cf9fb97e · 2025-07-01T12:18:22.000+02:00
The reproducer executes the host's unlocked_ioctl call in two different tasks. When init_context fails, the struct vmci_event_ctx is not fully initialized when executing vmci_datagram_dispatch() to send events to all vm contexts. This affects the datagram taken from the datagram queue of its context by another task, because the datagram payload is not initialized according to the size payload_size, which causes the kernel data to leak to the user space. Before dispatching the datagram, and before setting the payload content, explicitly set the payload content to 0 to avoid data leakage caused by incomplete payload initialization. Fixes: 28d6692 ("VMCI: context implementation.") Reported-by: syzbot+9b9124ae9b12d5af5d95@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=9b9124ae9b12d5af5d95 Tested-by: syzbot+9b9124ae9b12d5af5d95@syzkaller.appspotmail.com Signed-off-by: Lizhi Xu <lizhi.xu@windriver.com> Link: https://lore.kernel.org/r/20250627055214.2967129-1-lizhi.xu@windriver.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/misc/vmw_vmci/vmci_context.c b/drivers/misc/vmw_vmci/vmci_context.c
@@ -251,6 +251,8 @@ static int ctx_fire_notification(u32 context_id, u32 priv_flags)
 		ev.msg.hdr.src = vmci_make_handle(VMCI_HYPERVISOR_CONTEXT_ID,
 						  VMCI_CONTEXT_RESOURCE_ID);
 		ev.msg.hdr.payload_size = sizeof(ev) - sizeof(ev.msg.hdr);
+		memset((char*)&ev.msg.hdr + sizeof(ev.msg.hdr), 0,
+			ev.msg.hdr.payload_size);
 		ev.msg.event_data.event = VMCI_EVENT_CTX_REMOVED;
 		ev.payload.context_id = context_id;
 
