linux-kernel - RE: [PATCH -next 2/3] xen: balloon: Replaced simple

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Date:   Thu, 27 May 2021 14:10:21 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     'Chen Huang' <chenhuang5@...wei.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        "Paul Mackerras" <paulus@...ba.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Stefano Stabellini <sstabellini@...nel.org>,
        Mark Fasheh <mark@...heh.com>,
        Joel Becker <jlbec@...lplan.org>,
        Joseph Qi <joseph.qi@...ux.alibaba.com>,
        Nathan Lynch <nathanl@...ux.ibm.com>,
        "Andrew Donnellan" <ajd@...ux.ibm.com>,
        Alexey Kardashevskiy <aik@...abs.ru>,
        "Andrew Morton" <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Jens Axboe <axboe@...nel.dk>,
        Yang Yingliang <yangyingliang@...wei.com>,
        Masahiro Yamada <masahiroy@...nel.org>,
        Dan Carpenter <dan.carpenter@...cle.com>
CC:     "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
        "ocfs2-devel@....oracle.com" <ocfs2-devel@....oracle.com>
Subject: RE: [PATCH -next 2/3] xen: balloon: Replaced simple_strtoull() with
 kstrtoull()

From: Chen Huang
> Sent: 26 May 2021 10:20
> 
> The simple_strtoull() function is deprecated in some situation, since
> it does not check for the range overflow, use kstrtoull() instead.
> 
...
> -	target_bytes = simple_strtoull(buf, &endchar, 0) * 1024;
> +	ret = kstrtoull(buf, 0, &target_bytes);
> +	if (ret)
> +		return ret;
> +	target_bytes *= 1024;

I'd have thought it was more important to check *endchar
than overflow.
If you are worried about overflow you need a range check
before the multiply.

	David

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