Messages in this thread | | | Date | Fri, 28 Jun 2019 01:09:08 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH] ftrace: Remove possible deadlock between register_kprobe() and ftrace_run_update_code() |
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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
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