Re: [PATCH 1/1] stackleak: Disable ftrace for stackleak.c

[Alexander Popov]

On 11.11.2018 2:30, Steven Rostedt wrote:
> On Sun, 11 Nov 2018 01:05:30 +0300
> Alexander Popov <alex.popov@xxxxxxxxx> wrote:
> 
>> The stackleak_erase() function is called on the trampoline stack at the
>> end of syscall. This stack is not big enough for ftrace operations,
>> e.g. it can be overflowed if we enable kprobe_events for stackleak_erase().
> 
> Is the issue with kprobes or with function tracing? Because this stops
> function tracing which I only want disabled if function tracing itself
> is an issue, not for other things that may use the function tracing
> infrastructure.

Hello Steven,

I believe that stackleak erasing is not compatible with function tracing itself.
That's what the kernel testing robot has hit:
https://www.openwall.com/lists/kernel-hardening/2018/11/09/1

I used kprobe_events just to reproduce the problem:
https://www.openwall.com/lists/kernel-hardening/2018/11/09/4

Best regards,
Alexander