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Message-ID: <20190627211304.7e21fd77@gandalf.local.home>
Date: Thu, 27 Jun 2019 21:13:04 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Petr Mladek <pmladek@...e.com>,
Miroslav Benes <mbenes@...e.cz>, Jessica Yu <jeyu@...nel.org>,
Jiri Kosina <jikos@...nel.org>,
Joe Lawrence <joe.lawrence@...hat.com>,
linux-kernel@...r.kernel.org, live-patching@...r.kernel.org,
Johannes Erdfelt <johannes@...felt.com>,
Ingo Molnar <mingo@...nel.org>, mhiramat@...nel.org,
torvalds@...ux-foundation.org
Subject: Re: [PATCH] ftrace: Remove possible deadlock between
register_kprobe() and ftrace_run_update_code()
On Thu, 27 Jun 2019 18:19:52 -0500
Josh Poimboeuf <jpoimboe@...hat.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();
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