linux-kernel - Re: [PATCH] x86/kprobes: Fix 1 byte conditional jump target

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Date:   Wed, 8 Feb 2023 06:58:45 +0000
From:   Nadav Amit <namit@...are.com>
To:     Dave Hansen <dave.hansen@...el.com>
CC:     "Masami Hiramatsu (Google)" <mhiramat@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        X86 ML <x86@...nel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] x86/kprobes: Fix 1 byte conditional jump target



> On Feb 8, 2023, at 8:56 AM, Dave Hansen <dave.hansen@...el.com> wrote:
> 
> !! External Email
> 
> On 2/7/23 22:34, Nadav Amit wrote:
>> As you said, I guess the change you and Masami proposed can be done on top of
>> this patch, which is (and was) only intended to fix the bug, and should
>> therefore go into 6.2.
> 
> Nadav,
> 
> To fix this issue, you proposed:
> 
>        p->ainsn.rel32 = *(s8 *)&insn->immediate.value;
> 
> But, this is, um, rather obfuscated and potentially less correct
> compared to:
> 
>        p->ainsn.rel32 = insn->immediate.value;
> 
> I'd appreciate it if you could update your patch to do this simpler
> thing and resend, unless there is a strong reason to do what you
> originally proposed.

I thought it makes sense to make this change for all the other cases
in one pass, but whatever makes you happy.

I will send v2 soon.

Thanks again,
Nadav