linux-kernel - Re: [RFCv1 0/6] Page Detective

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Message-ID: <ZzzXqXGRlAwk-H2m@google.com>
Date: Tue, 19 Nov 2024 18:23:37 +0000
From: Roman Gushchin <roman.gushchin@...ux.dev>
To: Pasha Tatashin <pasha.tatashin@...een.com>
Cc: Greg KH <gregkh@...uxfoundation.org>, linux-kernel@...r.kernel.org,
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Subject: Re: [RFCv1 0/6] Page Detective

On Tue, Nov 19, 2024 at 10:08:36AM -0500, Pasha Tatashin wrote:
> On Mon, Nov 18, 2024 at 8:09 PM Greg KH <gregkh@...uxfoundation.org> wrote:
> >
> > On Mon, Nov 18, 2024 at 05:08:42PM -0500, Pasha Tatashin wrote:
> > > Additionally, using crash/drgn is not feasible for us at this time, it
> > > requires keeping external tools on our hosts, also it requires
> > > approval and a security review for each script before deployment in
> > > our fleet.
> >
> > So it's ok to add a totally insecure kernel feature to your fleet
> > instead?  You might want to reconsider that policy decision :)
> 
> Hi Greg,
> 
> While some risk is inherent, we believe the potential for abuse here
> is limited, especially given the existing  CAP_SYS_ADMIN requirement.
> But, even with root access compromised, this tool presents a smaller
> attack surface than alternatives like crash/drgn. It exposes less
> sensitive information, unlike crash/drgn, which could potentially
> allow reading all of kernel memory.

The problem here is with using dmesg for output. No security-sensitive
information should go there. Even exposing raw kernel pointers is not
considered safe.

I'm also not sure about what presents a bigger attack surface. Yes,
drgn allows to read more, but it's using /proc/kcore, so the in-kernel
code is much simpler. But I don't think it's a relevant discussion,
if a malicious user has a root access, there are better options than
both drgn and page detective.