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Date:   Fri, 22 May 2020 10:34:17 -0700
From:   Kees Cook <keescook@chromium.org>
To:     Petr Mladek <pmladek@suse.com>
Cc:     Pavel Tatashin <pasha.tatashin@soleen.com>,
        Anton Vorontsov <anton@enomsg.org>,
        Colin Cross <ccross@android.com>,
        Tony Luck <tony.luck@intel.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Benson Leung <bleung@chromium.org>,
        Rob Herring <robh+dt@kernel.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v4 2/6] printk: honor the max_reason field in kmsg_dumper
Message-ID: <202005221032.859452DFA0@keescook>
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 <20200515184434.8470-3-keescook@chromium.org>
 <20200522165120.GL3464@linux-b0ei>
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On Fri, May 22, 2020 at 06:51:20PM +0200, Petr Mladek wrote:
> On Fri 2020-05-15 11:44:30, Kees Cook wrote:
> > From: Pavel Tatashin <pasha.tatashin@soleen.com>
> > 
> > kmsg_dump() allows to dump kmesg buffer for various system events: oops,
> > panic, reboot, etc. It provides an interface to register a callback call
> > for clients, and in that callback interface there is a field "max_reason"
> > which gets ignored unless always_kmsg_dump is passed as kernel parameter.
> 
> Strictly speaking, this is not fully true. "max_reason" field is not
> ignored when set to KMSG_DUMP_PANIC even when always_kmsg_dump was not set.
> 
> It should be something like:
> 
> "which gets ignored for reason higher than KMSG_DUMP_OOPS unless
> always_kmsg_dump is passed as kernel parameter".
> 
> Heh, I wonder if anyone will be able to parse this ;-)

Ah yeah, good point. I've reworded things like this:


    kmsg_dump() allows to dump kmesg buffer for various system events: oops,
    panic, reboot, etc. It provides an interface to register a callback
    call for clients, and in that callback interface there is a field
    "max_reason", but it was getting ignored when set to any "reason"
    higher than KMSG_DUMP_OOPS unless "always_kmsg_dump" was passed as
    kernel parameter.

    Allow clients to actually control their "max_reason", and keep the
    current behavior when "max_reason" is not set.

> Otherwise, it looks good to me. With the updated commit message:
> 
> Reviewed-by: Petr Mladek <pmladek@suse.com>

Thanks!

-- 
Kees Cook