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SubjectRe: Oops caused by race between livepatch and ftrace
On Tue, 21 May 2019, Steven Rostedt wrote:

> > Hm. I suppose using ftrace_lock might be less risky since that lock
> > is only used internally by ftrace (up until now). But I think it
> > would also make less sense because the text_mutex is supposed to
> > protect code patching. And presumably ftrace_lock is supposed to be
> > ftrace-specific.
> >
> > Here's the latest patch, still using text_mutex. I added some lockdep
> > assertions to ensure the permissions toggling functions are always
> > called with text_mutex. It's running through 0-day right now. I can
> > try to run it through various tests with CONFIG_LOCKDEP.
>
> Yeah, text_mutex probably does make more sense. ftrace_mutex was around
> before text_mutex as ftrace was the first one to do the runtime
> patching (after boot has finished). It wasn't until we introduced
> text_poke that we decided to create the text_mutex locking as well.
>
> >
> >
> > From: Josh Poimboeuf <jpoimboe@redhat.com>
> > Subject: [PATCH] livepatch: Fix ftrace module text permissions race
>
> Thanks,
>
> I'll try to find some time to test this as well.

Steve, Jessica, any final word on this?

Thanks,

--
Jiri Kosina
SUSE Labs

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