linux-kernel - Re: [PATCH v2] kasan: Disable branch tracing for core runtime

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Message-Id: <20200522164247.4a88aed496f0feb458d8bca0@linux-foundation.org>
Date:   Fri, 22 May 2020 16:42:47 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Marco Elver <elver@...gle.com>
Cc:     dvyukov@...gle.com, glider@...gle.com, andreyknvl@...gle.com,
        linux-kernel@...r.kernel.org, kasan-dev@...glegroups.com,
        aryabinin@...tuozzo.com, linux-mm@...ck.org, cai@....pw,
        kernel test robot <rong.a.chen@...el.com>
Subject: Re: [PATCH v2] kasan: Disable branch tracing for core runtime

On Fri, 22 May 2020 09:52:07 +0200 Marco Elver <elver@...gle.com> wrote:

> During early boot, while KASAN is not yet initialized, it is possible to
> enter reporting code-path and end up in kasan_report(). While
> uninitialized, the branch there prevents generating any reports,
> however, under certain circumstances when branches are being traced
> (TRACE_BRANCH_PROFILING), we may recurse deep enough to cause kernel
> reboots without warning.
> 
> To prevent similar issues in future, we should disable branch tracing
> for the core runtime.
> 
> Link: https://lore.kernel.org/lkml/20200517011732.GE24705@shao2-debian/
> Reported-by: kernel test robot <rong.a.chen@...el.com>
> Signed-off-by: Marco Elver <elver@...gle.com>

I assume this affects 5.6 and perhaps earlier kernels?

I also assume that a cc:stable is appropriate for this fix?