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Date:   Tue, 26 Mar 2019 14:58:45 -0700
From:   Mike Travis <>
To:     Yuri Norov <>,
        Andy Shevchenko <>,
        Yury Norov <>
Cc:     Andrew Morton <>,
        Rasmus Villemoes <>,
        Arnd Bergmann <>,
        Kees Cook <>,
        Matthew Wilcox <>,
        Tetsuo Handa <>,
        "" <>,
        Mike Travis <>,
        Thomas Gleixner <>
Subject: Re: [PATCH 3/6] bitmap_parselist: rework input string parser

On 3/26/2019 2:09 PM, Yuri Norov wrote:
> + Mike Travis <>
> + Thomas Gleixner <>
> ----------------------------------------------------------------------
> On Tue, Mar 26, 2019 at 12:07:45AM +0300, Yury Norov wrote:
>>> The requirement for this rework is to keep the __bitmap_parselist()
>>> copy-less and single-pass but make it more readable and maintainable by
>>> splitting into logical parts and removing explicit nested cycles and
>>> opaque local variables.
>>> __bitmap_parselist() can parse userspace inputs and therefore we cannot
>>> use simple_strtoul() to parse numbers.
>> So, all above depends to what memory we access kernel / user space.
>> Perhaps we can get copy of memory of a given size and then parse it in kernel space always?
>> --
>> With Best Regards,
>> Andy Shevchenko
> What I missed during rework is that we have only one caller of *parselist_userĀ  -
> it's write_irq_affinity() introduced by Mike Travis in kernel/irq/proc.c. It doesn't look
> like a hot path as it's file operations handler. If no objections from Mike or Thomas,

No objections from me as long as you can still change irq affinity using 
a cpulist instead of a cpumask.

Mike Travis

> I think it would make sense to copy_from_user() the userspace data at the beginning
> in sake of simplicity of __bitmap_parselist(), as you suggested above.
> Yury

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