On Tue, 2 Jul 2019 22:18:27 +0200 Peter Zijlstra <pet...@infradead.org> wrote:
> 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 Oh, I wrote the patches. No wonder I couldn't find them in my local "patchwork". It doesn't include patches I write. But still, I completely forgot. Better send me to the nursing home :-p > > I think; lemme re-read that thread. I'll need to do that too. -- Steve
