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From:   Pingfan Liu <kernelfans@gmail.com>
Date:   Mon, 29 Apr 2019 11:04:49 +0800
Message-ID: <CAFgQCTvQezGM7xgY2Q1RSUiQ7wLdxtUAeztrO3AqDfjx8f2kdg@mail.gmail.com>
Subject: Re: [PATCHv2] kernel/crash: make parse_crashkernel()'s return value
 more indicant
To:     Dave Young <dyoung@redhat.com>
Cc:     Matthias Brugger <mbrugger@suse.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Rich Felker <dalias@libc.org>, linux-ia64@vger.kernel.org,
        Julien Thierry <julien.thierry@arm.com>,
        Yangtao Li <tiny.windzz@gmail.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
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        "H. Peter Anvin" <hpa@zytor.com>, linux-s390@vger.kernel.org,
        Florian Fainelli <f.fainelli@gmail.com>,
        Yoshinori Sato <ysato@users.sourceforge.jp>,
        linux-sh@vger.kernel.org, Michael Ellerman <mpe@ellerman.id.au>,
        David Hildenbrand <david@redhat.com>,
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On Sun, Apr 28, 2019 at 4:37 PM Dave Young <dyoung@redhat.com> wrote:
>
> On 04/25/19 at 04:20pm, Pingfan Liu wrote:
> > On Wed, Apr 24, 2019 at 4:31 PM Matthias Brugger <mbrugger@suse.com> wrote:
> > >
> > >
> > [...]
> > > > @@ -139,6 +141,8 @@ static int __init parse_crashkernel_simple(char *cmdline,
> > > >               pr_warn("crashkernel: unrecognized char: %c\n", *cur);
> > > >               return -EINVAL;
> > > >       }
> > > > +     if (*crash_size == 0)
> > > > +             return -EINVAL;
> > >
> > > This covers the case where I pass an argument like "crashkernel=0M" ?
> > > Can't we fix that by using kstrtoull() in memparse and check if the return value
> > > is < 0? In that case we could return without updating the retptr and we will be
> > > fine.
> > >
> > It seems that kstrtoull() treats 0M as invalid parameter, while
> > simple_strtoull() does not.
> >
> > If changed like your suggestion, then all the callers of memparse()
> > will treats 0M as invalid parameter. This affects many components
> > besides kexec.  Not sure this can be done or not.
>
> simple_strtoull is obsolete, move to kstrtoull is the right way.
>
> $ git grep memparse|wc
>     158     950   10479
>
> Except some documentation/tools etc there are still a log of callers
> which directly use the return value as the ull number without error
> checking.
>
> So it would be good to mark memparse as obsolete as well in
> lib/cmdline.c, and introduce a new function eg. kmemparse() to use
> kstrtoull,  and return a real error code, and save the size in an
> argument like &size.  Then update X86 crashkernel code to use it.
>
Thank for your good suggestion.

Regards,
Pingfan