The patch titled ptrace-simplify-ptrace_exit-ignoring_children-pathpatch fix has been added to the -mm tree. Its filename is ptrace-simplify-ptrace_exit-ignoring_children-pathpatch-fix.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: ptrace-simplify-ptrace_exit-ignoring_children-pathpatch fix From: Oleg Nesterov <oleg@xxxxxxxxxx> Somehow I didn't even try to think about false _negative_, and it is possible without ->siglock. If we race with sigaction() which changes ->action[SIGCHLD] from: { .sa_handler = SIG_IGN, .sa_flags = 0 } to: { .sa_handler = handler, .sa_flags = SA_NOCLDWAIT } we can read the stores out of order, and ignoring_children() may return the wrong "false". Nothing really bad can happen, and the race is mostly theoretical, but still this is not right. [PATCH 2/4] ptrace: simplify ptrace_exit()->ignoring_children() path In order to avoid the unnecessary ignoring_children() calls, ptrace_exit() uses "int ign" to cache the returned value. This makes sense because ptrace_exit() works with the list of tracees, but the next patche changes this code to work with individual threads. Remove this optimization, I don't think it is common to exit with a lot of attached EXIT_ZOMBIE tracees. And this makes the code a bit simpler. Also remove _irqsave/_irqrestore, this code always runs with irqs disabled. Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx> Cc: Jerome Marchand <jmarchan@xxxxxxxxxx> Cc: Roland McGrath <roland@xxxxxxxxxx> Cc: Denys Vlasenko <dvlasenk@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- kernel/exit.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff -puN kernel/exit.c~ptrace-simplify-ptrace_exit-ignoring_children-pathpatch-fix kernel/exit.c --- a/kernel/exit.c~ptrace-simplify-ptrace_exit-ignoring_children-pathpatch-fix +++ a/kernel/exit.c @@ -729,12 +729,16 @@ static void exit_mm(struct task_struct * } /* - * Return nonzero if childs should reap themselves. + * Called with irqs disabled, returns true if childs should reap themselves. */ static int ignoring_children(struct sighand_struct *sigh) { - return sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN || - sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT; + int ret; + spin_lock(&sigh->siglock); + ret = (sigh->action[SIGCHLD-1].sa.sa_handler == SIG_IGN) || + (sigh->action[SIGCHLD-1].sa.sa_flags & SA_NOCLDWAIT); + spin_unlock(&sigh->siglock); + return ret; } /* _ Patches currently in -mm which might be from oleg@xxxxxxxxxx are origin.patch wait-prevent-exclusive-waiter-starvation.patch linux-next.patch pipe_rdwr_fasync-fix-the-error-handling-to-prevent-the-leak-crash.patch get_mm_hiwater_xxx-trivial-s-define-inline.patch getrusage-fill-ru_maxrss-value.patch ptrace-kill-__ptrace_detach-fix-exit_state-check.patch ptrace-simplify-ptrace_exit-ignoring_children-path.patch ptrace-simplify-ptrace_exit-ignoring_children-pathpatch-fix.patch ptrace-reintroduce-__ptrace_detach-as-a-callee-of-ptrace_exit.patch ptrace-fix-possible-zombie-leak-on-ptrace_detach.patch reparent_thread-dont-call-kill_orphaned_pgrp-if-task_detached.patch reparent_thread-fix-the-is-it-traced-check.patch reparent_thread-fix-a-zombie-leak-if-sbin-init-ignores-sigchld.patch forget_original_parent-cleanup-ptrace-pathes.patch kthread-dont-looking-for-a-task-in-create_kthread-2.patch pids-document-task_pgrp-task_session-is-not-safe-without-tasklist-rcu.patch pids-document-task_pgrp-task_session-is-not-safe-without-tasklist-rcu-fix.patch pids-improve-get_task_pid-to-fix-the-unsafe-sys_wait4-task_pgrp.patch pids-refactor-vnr-nr_ns-helpers-to-make-them-safe.patch pids-kill-now-unused-signal_struct-__pgrp-__session-and-friends.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html