linux-kernel - Re: [PATCH 2/2] uprobes: x86: Prohibit probing on MOV SS instruction

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Date:   Wed, 9 May 2018 18:39:40 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Masami Hiramatsu <mhiramat@...nel.org>
Cc:     x86@...nel.org, LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Alexei Starovoitov <ast@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Steven Rostedt <rostedt@...dmis.org>,
        Francis Deslauriers <francis.deslauriers@...icios.com>,
        Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>,
        Borislav Petkov <bp@...e.de>, Yonghong Song <yhs@...com>
Subject: Re: [PATCH 2/2] uprobes: x86: Prohibit probing on MOV SS instruction

On 05/09, Masami Hiramatsu wrote:
>
> Since MOV SS and POP SS instructions will delay the exceptions
> until the next instruction is executed, we should not do
> single-stepping on it by uprobes.
...
> --- a/arch/x86/kernel/uprobes.c
> +++ b/arch/x86/kernel/uprobes.c
> @@ -299,6 +299,10 @@ static int uprobe_init_insn(struct arch_uprobe *auprobe, struct insn *insn, bool
>  	if (is_prefix_bad(insn))
>  		return -ENOTSUPP;
>  
> +	/* We should not singlestep on the exception masking instructions */
> +	if (insn_masking_exception(insn))
> +		return -ENOTSUPP;

Acked-by: Oleg Nesterov <oleg@...hat.com>