Re: [PATCH 1/3] module: Fix livepatch/ftrace module text permissions race

[Steven Rostedt]

On Thu, 13 Jun 2019 20:07:22 -0500
Josh Poimboeuf <jpoimboe@xxxxxxxxxx> wrote:

> It's possible for livepatch and ftrace to be toggling a module's text
> permissions at the same time, resulting in the following panic:
> 

[..]

> The above panic occurs when loading two modules at the same time with
> ftrace enabled, where at least one of the modules is a livepatch module:
> 
> CPU0					CPU1
> klp_enable_patch()
>   klp_init_object_loaded()
>     module_disable_ro()
>     					ftrace_module_enable()
> 					  ftrace_arch_code_modify_post_process()
> 				    	    set_all_modules_text_ro()
>       klp_write_object_relocations()
>         apply_relocate_add()
> 	  *patches read-only code* - BOOM
> 
> A similar race exists when toggling ftrace while loading a livepatch
> module.
> 
> Fix it by ensuring that the livepatch and ftrace code patching
> operations -- and their respective permissions changes -- are protected
> by the text_mutex.
> 
> Reported-by: Johannes Erdfelt <johannes@xxxxxxxxxxx>
> Fixes: 444d13ff10fb ("modules: add ro_after_init support")
> Signed-off-by: Josh Poimboeuf <jpoimboe@xxxxxxxxxx>
> Acked-by: Jessica Yu <jeyu@xxxxxxxxxx>
> Reviewed-by: Petr Mladek <pmladek@xxxxxxxx>
> Reviewed-by: Miroslav Benes <mbenes@xxxxxxx>

This patch looks uncontroversial. I'm going to pull this one in and
start testing it. And if it works, I'll push to Linus.

-- Steve