On 10/20, Andrew Morton wrote: > > On Tue, 20 Oct 2015 19:17:54 +0200 Oleg Nesterov <[email protected]> wrote: > > > The following program (simplified version of generated by syzkaller) > > > > #include <pthread.h> > > #include <unistd.h> > > #include <sys/ptrace.h> > > #include <stdio.h> > > #include <signal.h> > > > > void *thread_func(void *arg) > > { > > ptrace(PTRACE_TRACEME, 0,0,0); > > return 0; > > } > > > > int main(void) > > { > > pthread_t thread; > > > > if (fork()) > > return 0; > > > > while (getppid() != 1) > > ; > > > > pthread_create(&thread, NULL, thread_func, NULL); > > pthread_join(thread, NULL); > > return 0; > > } > > > > creates the unreapable zombie if /sbin/init doesn't use __WALL. > > > > This is not a kernel bug, at least in a sense that everything works as > > expected: debugger should reap a traced sub-thread before it can reap > > the leader, but without __WALL/__WCLONE do_wait() ignores sub-threads. > > > > Unfortunately, it seems that /sbin/init in most (all?) distributions > > doesn't use it and we have to change the kernel to avoid the problem. > > Well, to fix this a distro needs to roll out a new kernel. Or a new > init(8). Is there any reason to believe that distributing/deploying a > new kernel is significantly easier for everyone? Because fixing init > sounds like a much preferable solution to this problem.
I will be happy if we decide that this is userpace problem and we should not fix the kernel. I simply do not know. However, please look at 2/2 which imho makes sense regardless and looks "obviously safe". Without this patch waitid() can not use __WALL, so if /sbin/init uses waitid() then the userspace fix won't be one-liner. And at least Fedora22 and Ubuntu use waitid(). So personally I'd prefer 2/2 + fix-init, not sure if this can work... Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
