On Tue, 16 May 2017 14:58:35 -0400 Steven Rostedt <rost...@goodmis.org> wrote:
> From: Steven Rostedt (VMware) <rost...@goodmis.org> > > Thomas discovered a bug where the kprobe trace tests had a race > condition where the kprobe_optimizer called from a delayed work queue > that does the optimizing and "unoptimizing" of a kprobe, can try to > modify the text after it has been freed by the init code. > > The kprobe trace selftest is a special case, and Thomas and myself > investigated to see if there's a chance that this could also be a bug > with module unloading, as the code is not obvious to how it handles > this. After adding lots of printks, I figured it out. Thomas suggested > that this should be commented so that others will not have to go > through this exercise again. > OK, and I prefer this comment to move into kill_kprobe() right before calling kill_optimized_kprobe() because that actually does it. Thank you, > Suggested-by: Thomas Gleixner <t...@linutronix.de> > Signed-off-by: Steven Rostedt (VMware) <rost...@goodmis.org> > --- > diff --git a/kernel/kprobes.c b/kernel/kprobes.c > index 7367e0e..ac386f6 100644 > --- a/kernel/kprobes.c > +++ b/kernel/kprobes.c > @@ -2183,6 +2183,12 @@ static int kprobes_module_callback(struct > notifier_block *nb, > * The vaddr this probe is installed will soon > * be vfreed buy not synced to disk. Hence, > * disarming the breakpoint isn't needed. > + * > + * Note, this will also move any optimized > probes > + * that are pending to be removed from their > + * corresponding lists to the freeing_list and > + * will not be touched by the delayed > + * kprobe_optimizer work handler. > */ > kill_kprobe(p); > } -- Masami Hiramatsu <mhira...@kernel.org>
