linux-kernel - Re: [PATCH v2] x86/dumpstack: Fix misleading instruction pointer error message

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: <CALCETrW+Jek_t51RyqxO=HUA_PJ4APwS9hJQWsXyc426cgf0wA@mail.gmail.com>
Date:   Mon, 16 Nov 2020 15:04:02 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Borislav Petkov <bp@...en8.de>, Oleg Nesterov <oleg@...hat.com>,
        Mark Mossberg <mark.mossberg@...il.com>,
        Ingo Molnar <mingo@...hat.com>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "H. Peter Anvin" <hpa@...or.com>, Jann Horn <jannh@...gle.com>,
        kyin@...hat.com
Subject: Re: [PATCH v2] x86/dumpstack: Fix misleading instruction pointer
 error message

On Mon, Nov 16, 2020 at 2:01 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>  arch/x86/kernel/dumpstack.c |   23 +++++++++++++++++++----
>  1 file changed, 19 insertions(+), 4 deletions(-)
>
> --- a/arch/x86/kernel/dumpstack.c
> +++ b/arch/x86/kernel/dumpstack.c
> @@ -78,6 +78,9 @@ static int copy_code(struct pt_regs *reg
>         if (!user_mode(regs))
>                 return copy_from_kernel_nofault(buf, (u8 *)src, nbytes);
>
> +       /* The user space code from other tasks cannot be accessed. */
> +       if (regs != task_pt_regs(current))
> +               return -EPERM;

Depending on exactly where this gets called, this may not be
sufficient.  You should also check nmi_uaccess_okay().

--Andy