linux-kernel - Re: [PATCH] libfs: fix negative value support in simple_attr

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Message-ID: <f75a7d97-58cb-9136-093b-bf5af48da99a@amazon.com>
Date:   Tue, 20 Sep 2022 11:27:25 +0300
From:   "Farber, Eliav" <farbere@...zon.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
CC:     <viro@...iv.linux.org.uk>, <yangyicong@...ilicon.com>,
        <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <andriy.shevchenko@...el.com>, <hhhawa@...zon.com>,
        <jonnyc@...zon.com>, Akinobu Mita <akinobu.mita@...il.com>,
        "Farber, Eliav" <farbere@...zon.com>
Subject: Re: [PATCH] libfs: fix negative value support in simple_attr_write()

On 9/20/2022 12:24 AM, Andrew Morton wrote:
> On Sun, 18 Sep 2022 13:50:36 +0000 Eliav Farber <farbere@...zon.com> 
> wrote:
>
>> After commit 488dac0c9237 ("libfs: fix error cast of negative value in
>> simple_attr_write()"), a user trying set a negative value will get a
>> '-EINVAL' error, because simple_attr_write() was modified to use
>> kstrtoull() which can handle only unsigned values, instead of
>> simple_strtoll().
>>
>> This breaks all the places using DEFINE_DEBUGFS_ATTRIBUTE() with format
>> of a signed integer.
>>
>> The u64 value which attr->set() receives is not an issue for negative
>> numbers.
>> The %lld and %llu in any case are for 64-bit value. Representing it as
>> unsigned simplifies the generic code, but it doesn't mean we can't keep
>> their signed value if we know that.
>>
>> This change basically reverts the mentioned commit, but uses kstrtoll()
>> instead of simple_strtoll() which is obsolete.
>>
>
> https://lkml.kernel.org/r/20220919172418.45257-1-akinobu.mita@gmail.com
> addresses the same thing.
>
> Should the final version of this fix be backported into -stable trees?


I think that my patch can be dropped in favor of Akinobu's patch.

--
Regards, Eliav