On Mon, 13 Jun 2016 19:13:45 -0400 Steven Rostedt <rost...@goodmis.org> wrote:
> > # cd /sys/kernel/debug/tracing > > # echo p copy_user_enhanced_fast_string+5 > kprobe_events > > # echo 1 > events/kprobes/enable > > > > And you'll see a kernel panic on do_debug(), since the debug > > trap is not handled by kprobes. > > > > To fix this problem, we just need to clear the TF bit when > > resetting running kprobe. > > > > This should definitely be marked for stable, and I bisected it all the > way down to this commit: f4cb1cc18f364d "x86-64, copy_user: Remove zero > byte check before copy user buffer." > > I reverted that commit and sure enough, this bug goes away. I'm not > saying the revert should be done. I'm just doing an FYI, and showing how > changes that appear to be a nice clean up can have subtle effects. I'm > not even sure how that change caused this to be a problem with kprobes. > Nevermind, reverting that commit only moved the location of the "rep movsb" that you were placing the kprobe on. When I do: echo "p copy_user_enhanced_fast_string+9" > kprobe_events I get the same result. That means we need to make that stable tag even earlier. -- Steve
