From ed5d2cac114202fe2978a9cbcab8f5032796d538 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Mon, 4 Feb 2008 22:27:24 -0800 Subject: exec: rework the group exit and fix the race with kill As Roland pointed out, we have the very old problem with exec. de_thread() sets SIGNAL_GROUP_EXIT, kills other threads, changes ->group_leader and then clears signal->flags. All signals (even fatal ones) sent in this window (which is not too small) will be lost. With this patch exec doesn't abuse SIGNAL_GROUP_EXIT. signal_group_exit(), the new helper, should be used to detect exit_group() or exec() in progress. It can have more users, but this patch does only strictly necessary changes. Signed-off-by: Oleg Nesterov Cc: Davide Libenzi Cc: Ingo Molnar Cc: Robin Holt Cc: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- kernel/exit.c | 3 ++- kernel/signal.c | 4 ++-- 2 files changed, 4 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/exit.c b/kernel/exit.c index 9e459fefda7..9d3d0f0b27d 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -1083,11 +1083,12 @@ do_group_exit(int exit_code) struct signal_struct *const sig = current->signal; struct sighand_struct *const sighand = current->sighand; spin_lock_irq(&sighand->siglock); - if (sig->flags & SIGNAL_GROUP_EXIT) + if (signal_group_exit(sig)) /* Another thread got here before we took the lock. */ exit_code = sig->group_exit_code; else { sig->group_exit_code = exit_code; + sig->flags = SIGNAL_GROUP_EXIT; zap_other_threads(current); } spin_unlock_irq(&sighand->siglock); diff --git a/kernel/signal.c b/kernel/signal.c index 1117b28488c..6a5f97cd337 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -957,7 +957,6 @@ void zap_other_threads(struct task_struct *p) { struct task_struct *t; - p->signal->flags = SIGNAL_GROUP_EXIT; p->signal->group_stop_count = 0; for (t = next_thread(p); t != p; t = next_thread(t)) { @@ -1697,7 +1696,8 @@ static int do_signal_stop(int signr) } else { struct task_struct *t; - if (!likely(sig->flags & SIGNAL_STOP_DEQUEUED)) + if (!likely(sig->flags & SIGNAL_STOP_DEQUEUED) || + unlikely(sig->group_exit_task)) return 0; /* * There is no group stop already in progress. -- cgit v1.2.3