linux-kernel - Re: [PATCH] cpu/speculation: Warn on unsupported mitigations= parameter

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Message-ID: <20190516081627.GA109450@gmail.com>
Date:   Thu, 16 May 2019 10:16:27 +0200
From:   Ingo Molnar <mingo@...nel.org>
To:     Jiri Kosina <jikos@...nel.org>
Cc:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Ben Hutchings <ben@...adent.org.uk>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH] cpu/speculation: Warn on unsupported mitigations=
 parameter


* Jiri Kosina <jikos@...nel.org> wrote:

> On Thu, 16 May 2019, Geert Uytterhoeven wrote:
> 
> > Currently, if the user specifies an unsupported mitigation strategy on
> > the kernel command line, it will be ignored silently.  The code will
> > fall back to the default strategy, possibly leaving the system more
> > vulnerable than expected.
> 
> Honestly, I am not convinced. We are not doing this for vast majority of 
> other cmdline options either, if for any at all.

That's really a weakness - I've been bitten by this previously: I typoed 
or mis-remembered a command line option and didn't have it while I 
thought I had it.

Our boot-commandline library is pretty user-unfriendly.

Thanks,

	Ingo