linux-kernel - Re: [PATCH v2] x86/ioremap: Use is_ioremap

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Message-ID: <87le0zmhdp.fsf@nvdebian.thelocal>
Date: Wed, 14 Aug 2024 22:08:23 +1000
From: Alistair Popple <apopple@...dia.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: Christoph Hellwig <hch@...radead.org>, Max Ramanouski
 <max8rr8@...il.com>, x86@...nel.org, dave.hansen@...ux.intel.com,
 luto@...nel.org, peterz@...radead.org, linux-kernel@...r.kernel.org,
 jniethe@...dia.com, jhubbard@...dia.com, linux-mm@...ck.org
Subject: Re: [PATCH v2] x86/ioremap: Use is_ioremap_addr() in iounmap()


Thomas Gleixner <tglx@...utronix.de> writes:

> On Tue, Aug 13 2024 at 21:28, Christoph Hellwig wrote:
>> Modulo the fixes discussion (and any commit log adjustments related to
>> that), is_ioremap_addr is the right interface to check for an
>> ioremap address.  So for the actual code change:
>
> I'm not opposed to use is_ioremap_addr() as it restricts the check to
> the actual ioremp region.
>
> That said, I'm wondering why iounmap() silently bails out when invoked
> with an address which is outside of the ioremap region. I'd say, any
> invocation with an address outside of it, is broken, but I might be
> missing something as always.

I would tend to agree and had the same thought when we found this. At
least some kind of message (WARN_ON, WARN_ON_ONCE, printk, etc) would
have made the issue we were debugging much more obvious. FWIW I have
tested running with a WARN_ON() there and it never fired except in the
bug scenario.

 - Alistair

> Thanks,
>
>         tglx