linux-kernel - Re: [PATCH] x86/module: Fixed bug allowing invalid relocation addresses.

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Message-ID: <CAOQ9fa_p2_nrxaMFf5OZRXq-u+po9=UgpX-ss2FON4zCCrPb_w@mail.gmail.com>
Date:   Wed, 18 Mar 2020 21:46:35 +0200
From:   gilad kleinman <dkgs1998@...il.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] x86/module: Fixed bug allowing invalid relocation addresses.

When you load a bad module and the kernel crashes -- the panic message
will usually be related to the module and easily traced back. If you
load a module with a bad relocation table (because of a bit-flip \ bad
toolchain), it will override other kernel code, resulting in an
impossible to trace back kernel panic.

On Mon, Mar 16, 2020 at 2:58 PM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Sat, Mar 14, 2020 at 11:36:26PM +0200, Gilad Wharton Kleinman wrote:
> > If a kernel module with a bad relocation offset is loaded to a x86 kernel,
> > the kernel will apply the relocation to a address not inside the module
> > (resulting in memory in the kernel being overridden).
>
> Why !?
>
> If you load a bad module it's game over anyway. At best this protects us
> from broken toolchains.