linux-kernel - Re: [PATCH] lkdtm: avoid printk() in recursive

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Message-ID: <CAMj1kXFWE68Pozk4Kwqk_vYW96mrvz+XkbjXm-rTo=7ZA_BwTQ@mail.gmail.com>
Date:   Thu, 16 Dec 2021 12:16:19 +0100
From:   Ard Biesheuvel <ardb@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] lkdtm: avoid printk() in recursive_loop()

On Thu, 7 Oct 2021 at 18:59, Kees Cook <keescook@...omium.org> wrote:
>
> On Thu, 7 Oct 2021 10:12:35 +0200, Ard Biesheuvel wrote:
> > The recursive_loop() function is intended as a diagnostic to ensure that
> > exhausting the stack is caught and mitigated. Currently, it uses
> > pr_info() to ensure that the function has side effects that the compiler
> > cannot simply optimize away, so that the stack footprint does not get
> > reduced inadvertently.
> >
> > The typical mitigation for stack overflow is to kill the task, and this
> > overflow may occur inside the call to pr_info(), which means it could be
> > holding the console lock when this happens. This means that the console
> > lock is never going to be released again, preventing the diagnostic
> > prints related to the stack overflow handling from being visible on the
> > console.
> >
> > [...]
>
> Applied to for-next/lkdtm, thanks!
>
> [1/1] lkdtm: avoid printk() in recursive_loop()
>       https://git.kernel.org/kees/c/700fa7d22233
>

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