linux-kernel - Re: [patch V4 part 1 02/36] x86/hw_breakpoint: Prevent data breakpoints on cpu_entry

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Message-ID: <20200506081454.GA25532@zn.tnic>
Date:   Wed, 6 May 2020 10:14:54 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Andy Lutomirski <luto@...nel.org>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Will Deacon <will@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: Re: [patch V4 part 1 02/36] x86/hw_breakpoint: Prevent data
 breakpoints on cpu_entry_area

On Tue, May 05, 2020 at 03:16:04PM +0200, Thomas Gleixner wrote:
> From: Andy Lutomirski <luto@...nel.org>
> 
> A data breakpoint near the top of an IST stack will cause unresoverable

unrecoverable

> recursion.  A data breakpoint on the GDT, IDT, or TSS is terrifying.

"terrifying" huh? Colorful. :)

> Prevent either of these from happening.
> 
> Co-developed-by: Peter Zijlstra <peterz@...radead.org>
> Signed-off-by: Andy Lutomirski <luto@...nel.org>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
>  arch/x86/kernel/hw_breakpoint.c |   25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette