linux-kernel - Re: [PATCH] error-injection: Add prompt for function error injection

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Date:   Tue, 22 Nov 2022 07:24:04 +0900
From:   Masami Hiramatsu (Google) <mhiramat@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Kees Cook <keescook@...omium.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        KP Singh <kpsingh@...nel.org>, Chris Mason <clm@...a.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Florent Revest <revest@...omium.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Christoph Hellwig <hch@...radead.org>
Subject: Re: [PATCH] error-injection: Add prompt for function error
 injection

On Mon, 21 Nov 2022 10:44:03 -0500
Steven Rostedt <rostedt@...dmis.org> wrote:

> From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
> 
> The config to be able to inject error codes into any function annotated
> with ALLOW_ERROR_INJECTION() is enabled when CONFIG_FUNCTION_ERROR_INJECTION
> is enabled. But unfortunately, this is always enabled on x86 when KPROBES
> is enabled, and there's no way to turn it off.
> 
> As kprobes is useful for observability of the kernel, it is useful to have
> it enabled in production environments. But error injection should be
> avoided. Add a prompt to the config to allow it to be disabled even when
> kprobes is enabled, and get rid of the "def_bool y".
> 
> This is a kernel debug feature (it's in Kconfig.debug), and should have
> never been something enabled by default.
> 

Oops, thanks for update. Yes, it should not be enabled in the production system.

Acked-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Thanks,

> Cc: stable@...r.kernel.org
> Fixes: 540adea3809f6 ("error-injection: Separate error-injection from kprobe")
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
> ---
>  lib/Kconfig.debug | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index c3c0b077ade3..9ee72d8860c3 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -1874,8 +1874,14 @@ config NETDEV_NOTIFIER_ERROR_INJECT
>  	  If unsure, say N.
>  
>  config FUNCTION_ERROR_INJECTION
> -	def_bool y
> +	bool "Fault-injections of functions"
>  	depends on HAVE_FUNCTION_ERROR_INJECTION && KPROBES
> +	help
> +	  Add fault injections into various functions that are annotated with
> +	  ALLOW_ERROR_INJECTION() in the kernel. BPF may also modify the return
> +	  value of theses functions. This is useful to test error paths of code.
> +
> +	  If unsure, say N
>  
>  config FAULT_INJECTION
>  	bool "Fault-injection framework"
> -- 
> 2.35.1
> 


-- 
Masami Hiramatsu (Google) <mhiramat@...nel.org>