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Subject: Re: [PATCH] libfs: fix negative value support in simple_attr_write()
Message-ID: <f75a7d97-58cb-9136-093b-bf5af48da99a@amazon.com>
Date:   Tue, 20 Sep 2022 11:27:25 +0300
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To:     Andrew Morton <akpm@linux-foundation.org>
CC:     <viro@zeniv.linux.org.uk>, <yangyicong@hisilicon.com>,
        <linux-fsdevel@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
        <andriy.shevchenko@intel.com>, <hhhawa@amazon.com>,
        <jonnyc@amazon.com>, Akinobu Mita <akinobu.mita@gmail.com>,
        "Farber, Eliav" <farbere@amazon.com>
References: <20220918135036.33595-1-farbere@amazon.com>
 <20220919142413.c294de0777dcac8abe2d2f71@linux-foundation.org>
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From:   "Farber, Eliav" <farbere@amazon.com>
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On 9/20/2022 12:24 AM, Andrew Morton wrote:
> On Sun, 18 Sep 2022 13:50:36 +0000 Eliav Farber <farbere@amazon.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 instead of simple_strtoll() which is obsolete.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