linux-kernel - Re: [PATCH 1/2] x86/crash: Disable virt in core NMI crash handler to avoid double list

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87k0aqvjit.ffs@tglx>
Date:   Thu, 12 May 2022 17:48:58 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Sean Christopherson <seanjc@...gle.com>
Cc:     Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        "Guilherme G . Piccoli" <gpiccoli@...lia.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [PATCH 1/2] x86/crash: Disable virt in core NMI crash handler
 to avoid double list_add

On Thu, May 12 2022 at 14:14, Sean Christopherson wrote:
> On Thu, May 12, 2022, Thomas Gleixner wrote:
> diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c
> index 4e3a839ae146..808d3e75fb2d 100644
> --- a/arch/x86/kernel/reboot.c
> +++ b/arch/x86/kernel/reboot.c
> @@ -896,7 +896,11 @@ void nmi_shootdown_cpus(nmi_shootdown_cb callback)
>                 msecs--;
>         }
>  
> -       /* Leave the nmi callback set */
> +       /*
> +        * Leave the nmi callback set, shootdown is a one-time thing.  Clearing
> +        * the callback could result in a NULL pointer dereference if a CPU
> +        * (finally) responds after the timeout expires.
> +        */

Good point!