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

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Message-ID: <20221121104403.1545f9b5@gandalf.local.home>
Date:   Mon, 21 Nov 2022 10:44:03 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     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: [PATCH] error-injection: Add prompt for function error injection

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.

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