linux-kernel - Re: [PATCH] usercopy: Do not fail on memory from former init sections

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Message-Id: <20220107154430.1bd6252e66baada7d84bdd6c@linux-foundation.org>
Date:   Fri, 7 Jan 2022 15:44:30 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Helge Deller <deller@....de>
Cc:     Linux Kernel <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
        linux-parisc@...r.kernel.org
Subject: Re: [PATCH] usercopy: Do not fail on memory from former init
 sections

On Fri, 7 Jan 2022 01:19:24 +0100 Helge Deller <deller@....de> wrote:

> On some platforms the memory area between the _stext and the _etext
> symbols includes the init sections (parisc and csky). If the init
> sections are freed after bootup, the kernel may reuse this memory.
> 
> In one test the usercopy checks if the given address is inside the .text
> section (from _stext to _etext), and it wrongly fails on the mentioned
> platforms if the memory is from the former init section.
> 
> Fix this failure by first checking against the init sections before
> checking against the _stext/_etext section.

This sounds like it might have very serious runtime effects?

Please always fully describe a bug's runtime effects when fixing that bug.

> Fixes: 98400ad75e95 ("parisc: Fix backtrace to always include init funtion names")

So is this a must-have for 5.16?