linux-kernel - Re: [tip: x86/bugs] x86/retpoline: Ensure default return thunk isn't used at runtime

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Message-ID: <20231018151245.GCZS/17QhDGe7q6K+w@fat_crate.local>
Date:   Wed, 18 Oct 2023 17:12:45 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-tip-commits@...r.kernel.org,
        David Kaplan <david.kaplan@....com>,
        Josh Poimboeuf <jpoimboe@...nel.org>,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>, x86@...nel.org
Subject: Re: [tip: x86/bugs] x86/retpoline: Ensure default return thunk isn't
 used at runtime

On Wed, Oct 18, 2023 at 03:38:56PM +0200, Ingo Molnar wrote:
> If then WARN_ONCE().

WARN_ONCE() is not enough considering that if this fires, it means we're
not really properly protected against one of those RET-speculation
things.

It needs to be warning constantly but then still allow booting. I.e,
a ratelimited warn of sorts but I don't think we have that... yet.

-- 
Regards/Gruss,
    Boris.

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