From: Peter Zijlstra <peterz@infradead.org>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Andi Kleen <andi@firstfloor.org>,
x86@kernel.org, keescook@chromium.org,
linux-kernel@vger.kernel.org, sashal@kernel.org,
Andi Kleen <ak@linux.intel.com>,
stable@vger.kernel.org
Subject: Re: [PATCH v1] x86: Pin cr4 FSGSBASE
Date: Tue, 26 May 2020 11:17:45 +0200 [thread overview]
Message-ID: <20200526091745.GC325280@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200526081752.GA2650351@kroah.com>
On Tue, May 26, 2020 at 10:17:52AM +0200, Greg KH wrote:
> On Tue, May 26, 2020 at 09:57:36AM +0200, Peter Zijlstra wrote:
> > On Tue, May 26, 2020 at 08:56:18AM +0200, Greg KH wrote:
> > > On Mon, May 25, 2020 at 10:28:48PM -0700, Andi Kleen wrote:
> > > > From: Andi Kleen <ak@linux.intel.com>
> > > >
> > > > Since there seem to be kernel modules floating around that set
> > > > FSGSBASE incorrectly, prevent this in the CR4 pinning. Currently
> > > > CR4 pinning just checks that bits are set, this also checks
> > > > that the FSGSBASE bit is not set, and if it is clears it again.
> > >
> > > So we are trying to "protect" ourselves from broken out-of-tree kernel
> > > modules now? Why stop with this type of check, why not just forbid them
> > > entirely if we don't trust them? :)
> >
> > Oh, I have a bunch of patches pending for that :-)
>
> Ah, I thought I had seen something like that go by a while ago.
>
> It's sad that we have to write a "don't do stupid things" checker for
> kernel modules now :(
Because people... they get stuff from the interweb and run it :/ The
days that admins actually knew what they're doing is long long gone.
> > It will basically decode the module text and refuse to load the module
> > for most CPL0 instruction.
>
> Ok, so why would Andi's patch even be needed then? Andi, why post this?
Andi's patch cures a particularly bad module that floats around that
people use, probably without being aware that it's an insta-root hole.
My patches will be a while (too many things in the fire :/) and will
certainly not be for stable.
next prev parent reply other threads:[~2020-05-26 9:22 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-26 5:28 [PATCH v1] x86: Pin cr4 FSGSBASE Andi Kleen
2020-05-26 6:56 ` Greg KH
2020-05-26 7:57 ` Peter Zijlstra
2020-05-26 8:17 ` Greg KH
2020-05-26 9:17 ` Peter Zijlstra [this message]
2020-05-26 10:16 ` Greg KH
2020-05-26 15:48 ` Andi Kleen
2020-05-26 16:20 ` Kees Cook
2020-05-26 16:32 ` Greg KH
2020-05-26 17:24 ` Wojtek Porczyk
2020-05-27 7:07 ` Greg KH
2020-05-27 10:58 ` Wojtek Porczyk
2020-05-26 16:15 ` Kees Cook
2020-05-26 21:16 ` Greg KH
2020-05-26 16:38 ` Kees Cook
2020-05-26 23:14 ` Andi Kleen
2020-05-27 10:31 ` Peter Zijlstra
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