lkml.org 
[lkml]   [2019]   [Jun]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] ftrace: Remove possible deadlock between register_kprobe() and ftrace_run_update_code()
On Thu, 27 Jun 2019, Steven Rostedt wrote:
> On Thu, 27 Jun 2019 17:47:29 -0500
> > Releasing the lock in a separate function seems a bit surprising and
> > fragile, would it be possible to do something like this instead?
> >
> > diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> > index b38c388d1087..89ea1af6fd13 100644
> > --- a/arch/x86/kernel/ftrace.c
> > +++ b/arch/x86/kernel/ftrace.c
> > @@ -37,15 +37,21 @@
> > int ftrace_arch_code_modify_prepare(void)
> > {
> > mutex_lock(&text_mutex);
> > +
> > set_kernel_text_rw();
> > set_all_modules_text_rw();
> > +
> > + mutex_unlock(&text_mutex);
> > return 0;
> > }
> >
> > int ftrace_arch_code_modify_post_process(void)
> > {
> > + mutex_lock(&text_mutex);
> > +
> > set_all_modules_text_ro();
> > set_kernel_text_ro();
> > +
> > mutex_unlock(&text_mutex);
> > return 0;
> > }
>
> I agree with Josh on this. As the original bug was the race between
> ftrace and live patching / modules changing the text from ro to rw and
> vice versa. Just protecting the update to the text permissions is more
> robust, and should be more self documenting when we need to handle
> other architectures for this.

How is that supposed to work?

ftrace
prepare()
setrw()
setro()
patch <- FAIL

Thanks,

tglx

\
 
 \ /
  Last update: 2019-06-28 01:10    [W:0.138 / U:0.088 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site