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SubjectRe: Oops caused by race between livepatch and ftrace
On Tue, 21 May 2019 11:42:27 -0500
Josh Poimboeuf <> 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 <>
> Subject: [PATCH] livepatch: Fix ftrace module text permissions race


I'll try to find some time to test this as well.

-- Steve

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