linux-kernel - Re: [PATCH 6 of 7] x86: use early_ioremap in __acpi_map

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <48C7FA91.9050302@goop.org>
Date:	Wed, 10 Sep 2008 09:49:21 -0700
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	Ingo Molnar <mingo@...e.hu>
CC:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH 6 of 7] x86: use early_ioremap in __acpi_map_table

Ingo Molnar wrote:
>> So i'd suggest a different, more carful approach: keep the new code 
>> you wrote, but print a WARN()ing if prev_map is not unmapped yet when 
>> the next mapping is acquired. That way the ACPI code can be fixed 
>> gradually and without breaking existing functionality.
>>     
>
> ok, i stuck in your patches into tip/master today and -tip testing 
> quickly found an early-ioremap leak:
>
> [   36.625100] calling  check_early_ioremap_leak+0x0/0x3d
> [   36.630253] ------------[ cut here ]------------
> [   36.634884] WARNING: at arch/x86/mm/ioremap.c:577 check_early_ioremap_leak+0x28/0x3d()
> [   36.642811] Debug warning: early ioremap leak of 1 areas detected.
>
> find the full log below with ioremap-leak-tracing turned on. I've 
> excluded these commits for now from tip/master.
>   

Yes, that leak is expected, unfortunately.  __acpi_map_table() has no
corresponding unmap, and only maintains one mapping.  So it will leak
its last mapping when it switches over from using __acpi_map_table() to
ioremap().

So, yes, its ugly, but its guaranteed to be a single leaked mapping. 
But I'm not sure what the best approach to deal with it is.

(All those other backtraces are just informational, right?)

    J
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/