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

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Message-Id: <163362596339.2313433.1892710945535449841.b4-ty@chromium.org>
Date:   Thu,  7 Oct 2021 09:59:27 -0700
From:   Kees Cook <keescook@...omium.org>
To:     linux-kernel@...r.kernel.org, Ard Biesheuvel <ardb@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH] lkdtm: avoid printk() in recursive_loop()

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

-- 
Kees Cook