Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Fri, 22 May 2020 16:42:47 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Marco Elver <elver@google.com>
Cc:     dvyukov@google.com, glider@google.com, andreyknvl@google.com,
        linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com,
        aryabinin@virtuozzo.com, linux-mm@kvack.org, cai@lca.pw,
        kernel test robot <rong.a.chen@intel.com>
Subject: Re: [PATCH v2] kasan: Disable branch tracing for core runtime
Message-Id: <20200522164247.4a88aed496f0feb458d8bca0@linux-foundation.org>
In-Reply-To: <20200522075207.157349-1-elver@google.com>
References: <20200522075207.157349-1-elver@google.com>
Mime-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Fri, 22 May 2020 09:52:07 +0200 Marco Elver <elver@google.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@intel.com>
> Signed-off-by: Marco Elver <elver@google.com>

I assume this affects 5.6 and perhaps earlier kernels?

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