On 08/10, Kees Cook wrote: > > This fixes a ptrace vs fatal pending signals bug as manifested in seccomp > now that ptrace was reordered to happen after ptrace. The short version is > that seccomp should not attempt to call do_exit() while fatal signals are > pending under a tracer. This was needlessly paranoid. Instead, the syscall > can just be skipped and normal signal handling, tracer notification, and > process death can happen.
ACK. I think this change is fine in any case, but... > The bug happens because when __seccomp_filter() detects > fatal_signal_pending(), it calls do_exit() without dequeuing the fatal > signal. When do_exit() sends the PTRACE_EVENT_EXIT I _never_ understood what PTRACE_EVENT_EXIT should actually do. I mean, when it should actually stop. This was never defined. > notification and > that task is descheduled, __schedule() notices that there is a fatal > signal pending and changes its state from TASK_TRACED to TASK_RUNNING. And this can happen anyway, with or without this change, with or without seccomp. Because another fatal signal can be pending. So PTRACE_EVENT_EXIT actually depends on /dev/random. Perhaps we should finally define what it should do. Say, it should only stop if SIGKILL was sent "implicitely" by exit/exec. But as for exec, there are more (off-topic) complications, not sure we actually want this... Nevermind, the main problem is that _any_ change in this area can break something. This code is sooooooo old. But let me repeat, I think this change is fine anyway. Acked-by: Oleg Nesterov <[email protected]>
