On Fri, Aug 28, 2020 at 02:11:18PM +0000, Eddy_Wu@xxxxxxxxxxxxxx wrote: > > From: Masami Hiramatsu <mhiramat@xxxxxxxxxx> > > > > OK, schedule function will be the key. I guess the senario is.. > > > > 1) kretporbe replace the return address with kretprobe_trampoline on task1's kernel stack > > 2) the task1 forks task2 before returning to the kretprobe_trampoline > > 3) while copying the process with the kernel stack, task2->kretprobe_instances.first = NULL > > I think new process created by fork/clone uses a brand new kernel > stack? I thought only user stack are copied. Otherwise any process > launch should crash in the same way I was under the same impression, we create a brand new stack-frame for the new task, this 'fake' frame we can schedule into. It either points to ret_from_fork() for new user tasks, or kthread_frame_init() for kernel threads.
