From: Oleg Nesterov Date: Fri, 8 Feb 2008 12:19:00 +0000 (-0800) Subject: ptrace_stop: fix the race with ptrace detach+attach X-Git-Tag: firefly_0821_release~22723 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=6405f7f4675884b671bee66678e1c2859bdb0e56;p=firefly-linux-kernel-4.4.55.git ptrace_stop: fix the race with ptrace detach+attach If the tracer went away (may_ptrace_stop() failed), ptrace_stop() drops tasklist and then changes the ->state from TASK_TRACED to TASK_RUNNING. This can fool another tracer which attaches to us in between. Change the ->state under tasklist_lock to ensure that ptrace_check_attach() can't wrongly succeed. Also, remove the unnecessary mb(). Signed-off-by: Oleg Nesterov Acked-by: Roland McGrath Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/kernel/signal.c b/kernel/signal.c index 6d6d1ab39e7e..678bffa437c1 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -1638,11 +1638,11 @@ static void ptrace_stop(int exit_code, int nostop_code, siginfo_t *info) } else { /* * By the time we got the lock, our tracer went away. - * Don't stop here. + * Don't drop the lock yet, another tracer may come. */ - read_unlock(&tasklist_lock); - set_current_state(TASK_RUNNING); + __set_current_state(TASK_RUNNING); current->exit_code = nostop_code; + read_unlock(&tasklist_lock); } /*