On Tue, Jul 02, 2019 at 01:39:05PM -0400, Steven Rostedt wrote: > On Tue, 2 Jul 2019 11:33:55 -0400 > Steven Rostedt <rost...@goodmis.org> wrote: > > > On Tue, 2 Jul 2019 16:14:05 +0200 (CEST) > > Thomas Gleixner <t...@linutronix.de> wrote: > > > > > On Tue, 2 Jul 2019, Peter Zijlstra wrote: > > > > > > > On Tue, Jul 02, 2019 at 02:31:51PM +0900, Eiichi Tsukata wrote: > > > > > Put the boundary check before it accesses user space to prevent > > > > > unnecessary > > > > > access which might crash the machine. > > > > > > > > > > Especially, ftrace preemptirq/irq_disable event with user stack trace > > > > > option can trigger SEGV in pid 1 which leads to panic. > > > > Note, I'm only able to trigger this crash with the irq_disable event. > > The irq_enable and preempt_disable/enable events work just fine. This > > leads me to believe that the TRACE_IRQS_OFF macro (which uses a thunk > > trampoline) may have some issues and is probably the place to look at. > > I figured it out. > > It's another "corruption of the cr2" register issue. The following
Arrggghhh.. > patch makes the issue go away. I'm not suggesting that we use this > patch, but it shows where the bug lies. > > IIRC, there was patches posted before that fixed this issue. I'll go > look to see if I can dig them up. Was it Joel that sent them? https://lkml.kernel.org/r/20190320221534.165ab...@oasis.local.home I think; lemme re-read that thread.
