Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> writes: > On Mon, Jun 21, 2021 at 4:23 PM Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: >> >> How would it help e.g. oopsen on the way out of timer interrupts? >> IMO we simply shouldn't allow ptrace access if the tracee is in that kind >> of state, on any architecture... > > Yeah no, we can't do the "wait for ptrace" when the exit is due to an > oops. Although honestly, we have other cases like that where do_exit() > isn't 100% robust if you kill something in an interrupt. Like all the > locks it leaves locked etc. > > So do_exit() from a timer interrupt is going to cause problems > regardless. I agree it's probably a good idea to try to avoid causing > even more with the odd ptrace thing, but I don't think ptrace_event is > some really "fundamental" problem at that point - it's just one detail > among many many. > > So I was more thinking of the debug patch for m68k to catch all the > _regular_ cases, and all the other random cases of ptrace_event() or > ptrace_notify(). > > Although maybe we've really caught them all. The exit case was clearly > missing, and the thread fork case was scrogged. There are patches for > the known problems. The patches I really don't like are the > verification ones to find any unknown ones.. We still have nios2 which copied the m68k logic at some point. I think that is a processor that is still ``shipping'' and that people might still be using in new designs. I haven't looked closely enough to see what the other architectures with caller saved registers are doing. The challenging ones are /proc/pid/syscall and seccomp which want to see all of the system call arguments. I think every architecture always saves the system call arguments unconditionally, so those cases are probably not as interesting. But they certain look like they could be trouble. Eric
