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

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Message-Id: <20220919142413.c294de0777dcac8abe2d2f71@linux-foundation.org>
Date:   Mon, 19 Sep 2022 14:24:13 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Eliav Farber <farbere@...zon.com>
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>
Subject: Re: [PATCH] libfs: fix negative value support in
 simple_attr_write()

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 instead of simple_strtoll() which is obsolete.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?