On 11/28, Dmitry V. Levin wrote: > > > Just like ptrace_request(PTRACE_LISTEN) > > does but you can do this lockless (no need to lock_task_sighand()). > > Why this can be done lockless? All other places in that file do > the locking, PTRACE_LISTEN too doesn't need lock_task_sighand() to access ->last_siginfo, this code predates ptrace_freeze_traced() which ensures that the tracee can't go away and clear ->last_siginfo. However, unlike ptrace_get_syscall(), PTRACE_LISTEN needs spin_lock_irq(siglock), it modifies ->jobctl and calls signal_wake_up(). > > Of course, debugger can do PTRACE_SETSIGINFO and confuse itself but probably we > > do not care? > > The only potential issue I could think of is whether PTRACE_SETSIGINFO > could be used this way to cause an information leak by making > PTRACE_GET_SYSCALL_INFO access some unrelated data. Well, afaics ptrace_get_syscall() does nothing "special", debugger can use other PTRACE_ requests to get the same info? Oleg.
