From 3f17da699431ec48540beabc55c54d4b5e66c8e7 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Wed, 15 Feb 2006 22:13:24 +0300 Subject: [PATCH] [PATCH] fix kill_proc_info() vs CLONE_THREAD race There is a window after copy_process() unlocks ->sighand.siglock and before it adds the new thread to the thread list. In that window __group_complete_signal(SIGKILL) will not see the new thread yet, so this thread will start running while the whole thread group was supposed to exit. I beleive we have another good reason to place attach_pid(PID/TGID) under ->sighand.siglock. We can do the same for release_task()->__unhash_process() de_thread()->switch_exec_pids() After that we don't need tasklist_lock to iterate over the thread list, and we can simplify things, see for example do_sigaction() or sys_times(). Signed-off-by: Oleg Nesterov Cc: Roland McGrath Cc: Ingo Molnar Signed-off-by: Linus Torvalds --- kernel/fork.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/kernel/fork.c b/kernel/fork.c index 8e88b374cee9..3683ce10f4a9 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1123,8 +1123,8 @@ static task_t *copy_process(unsigned long clone_flags, p->real_parent = current; p->parent = p->real_parent; + spin_lock(¤t->sighand->siglock); if (clone_flags & CLONE_THREAD) { - spin_lock(¤t->sighand->siglock); /* * Important: if an exit-all has been started then * do not create this new thread - the whole thread @@ -1162,8 +1162,6 @@ static task_t *copy_process(unsigned long clone_flags, */ p->it_prof_expires = jiffies_to_cputime(1); } - - spin_unlock(¤t->sighand->siglock); } /* @@ -1189,6 +1187,7 @@ static task_t *copy_process(unsigned long clone_flags, nr_threads++; total_forks++; + spin_unlock(¤t->sighand->siglock); write_unlock_irq(&tasklist_lock); proc_fork_connector(p); return p; -- 2.20.1