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SubjectRe: [PATCH] ftrace: Remove possible deadlock between register_kprobe() and ftrace_run_update_code()
On Thu, Jun 27, 2019 at 09:13:04PM -0400, Steven Rostedt wrote:
> On Thu, 27 Jun 2019 18:19:52 -0500
> Josh Poimboeuf <jpoimboe@redhat.com> wrote:
>
>
> > Maybe a comment or two would help though.
> >
>
> I'm adding the following change. Care to add a "reviewed-by" for this
> one?
>
> -- Steve
>
> diff --git a/arch/x86/kernel/ftrace.c b/arch/x86/kernel/ftrace.c
> index 33786044d5ac..d7e93b2783fd 100644
> --- a/arch/x86/kernel/ftrace.c
> +++ b/arch/x86/kernel/ftrace.c
> @@ -36,6 +36,11 @@
>
> int ftrace_arch_code_modify_prepare(void)
> {
> + /*
> + * Need to grab text_mutex to prevent a race from module loading
> + * and live kernel patching from changing the text permissions while
> + * ftrace has it set to "read/write".
> + */
> mutex_lock(&text_mutex);
> set_kernel_text_rw();
> set_all_modules_text_rw();

For the patch+comment:

Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>

--
Josh

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