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. -- Steve > > It triggers segfaults in random user processes which is bad enough. > > And even with that 'fix' applied I can see random segfaults just less > frequent. > > > > RIP: 0033:0x55be7ad1c89f > > > Code: Bad RIP value. > > > > ^^^ that's weird, no amount of unwinding should affect regs->ip. > >
