linux-kernel - Re: [PATCH 2/2] reboot: fix parsing of reboot cpu number

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Message-ID: <202010161226.B136CDC8@keescook>
Date:   Fri, 16 Oct 2020 12:26:54 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Matteo Croce <mcroce@...ux.microsoft.com>
Cc:     linux-kernel@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>,
        Petr Mladek <pmladek@...e.com>, Arnd Bergmann <arnd@...db.de>,
        Mike Rapoport <rppt@...nel.org>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Robin Holt <robinmholt@...il.com>,
        Fabian Frederick <fabf@...net.be>, stable@...r.kernel.org
Subject: Re: [PATCH 2/2] reboot: fix parsing of reboot cpu number

On Fri, Oct 16, 2020 at 08:09:07PM +0200, Matteo Croce wrote:
> From: Matteo Croce <mcroce@...rosoft.com>
> 
> The kernel cmdline reboot= argument allows to specify the CPU used
> for rebooting, with the syntax `s####` among the other flags, e.g.
> 
>   reboot=soft,s4
>   reboot=warm,s31,force
> 
> In the early days the parsing was done with simple_strtoul(), later
> deprecated in favor of the safer kstrtoint() which handles overflow.
> 
> But kstrtoint() returns -EINVAL if there are non-digit characters
> in a string, so if this flag is not the last given, it's silently
> ignored as well as the subsequent ones.
> 
> To fix it, revert the usage of simple_strtoul(), which is no longer
> deprecated, and restore the old behaviour.

It is? Is there a reference, because this was never updated:
https://www.kernel.org/doc/html/latest/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull

-- 
Kees Cook