Hi! > > do_debug is a bit of a red herring here. ptrace should not be able to > > put a breakpoint on a kernel address, period. I would just pick a > > fixed address that's in the kernel text range or even just in the > > pre-KASLR text range and make sure it gets rejected. Maybe try a few > > different addresses for good measure. > > I've looked at the code and it seems like this would be a bit more > complicated since the breakpoint is set by an accident in a race and the > call still fails. Which is why the test triggers the breakpoint and > causes infinite loop in the kernel... > > I guess that we could instead read back the address with > PTRACE_PEEKUSER, so something as: > > > break_addr = ptrace(PTRACE_PEEKUSER, child_pid, > (void *)offsetof(struct user, u_debugreg[0]), > NULL); > > if (break_addr == kernel_addr) > tst_res(TFAIL, "ptrace() set break on a kernel address");
So this works actually nicely, even better than the original code. Any hints on how to select a fixed address in the kernel range as you pointed out in one of the previous emails? I guess that this would end up as a per-architecture mess of ifdefs if we wanted to hardcode it. -- Cyril Hrubis chru...@suse.cz
