linux-kernel - Re: [PATCH -tip v2 3/3] [BUGFIX] kprobes: Prohibit probing on func_ptr_is_kernel

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Date:	Fri, 1 Nov 2013 09:57:31 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	x86@...nel.org, lkml <linux-kernel@...r.kernel.org>,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Borislav Petkov <bp@...e.de>
Subject: Re: [PATCH -tip v2 3/3] [BUGFIX] kprobes: Prohibit probing on
 func_ptr_is_kernel_text

On Fri, 01 Nov 2013 11:25:37 +0000
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com> wrote:

> Prohibit probing on func_ptr_is_kernel_text().
> Since the func_ptr_is_kernel_text() is called from
> notifier_call_chain() which is called from int3 handler,
> probing it may cause double int3 fault and kernel will
> reboot.
> 
> This happenes when the kernel built with CONFIG_DEBUG_NOTIFIERS=y.

Reviewed-by: Steven Rostedt <rostedt@...dmis.org>

-- Steve

> 
> Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: "Uwe Kleine-König" <u.kleine-koenig@...gutronix.de>
> Cc: Borislav Petkov <bp@...e.de>
> Cc: Ingo Molnar <mingo@...nel.org>
> ---
>  kernel/extable.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/extable.c b/kernel/extable.c
> index 832cb28..022fb25 100644
> --- a/kernel/extable.c
> +++ b/kernel/extable.c
> @@ -129,7 +129,7 @@ int kernel_text_address(unsigned long addr)
>   * pointer is part of the kernel text, we need to do some
>   * special dereferencing first.
>   */
> -int func_ptr_is_kernel_text(void *ptr)
> +int nokprobe func_ptr_is_kernel_text(void *ptr)
>  {
>  	unsigned long addr;
>  	addr = (unsigned long) dereference_function_descriptor(ptr);
> 

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