linux-kernel - Re: [PATCH 2/2] trace: kdb: Replace simple_strtoul with kstrtoul in kdb

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Message-ID: <CAD=FV=W7K5d8Dg+W5qaB_Kg8LuzMdMFEKZ2FfFC3qp2xAPMfKA@mail.gmail.com>
Date:   Wed, 6 Dec 2023 07:17:25 -0800
From:   Doug Anderson <dianders@...omium.org>
To:     Daniel Thompson <daniel.thompson@...aro.org>
Cc:     Yuran Pereira <yuran.pereira@...mail.com>,
        kgdb-bugreport@...ts.sourceforge.net,
        linux-trace-kernel@...r.kernel.org, jason.wessel@...driver.com,
        rostedt@...dmis.org, mhiramat@...nel.org,
        linux-kernel@...r.kernel.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH 2/2] trace: kdb: Replace simple_strtoul with kstrtoul in kdb_ftdump

Hi,

On Wed, Dec 6, 2023 at 3:38 AM Daniel Thompson
<daniel.thompson@...aro.org> wrote:
>
> On Tue, Dec 05, 2023 at 01:41:57PM -0800, Doug Anderson wrote:
> > Hi,
> >
> > On Sun, Nov 19, 2023 at 4:10 PM Yuran Pereira <yuran.pereira@...mail.com> wrote:
> > >
> > > The function simple_strtoul performs no error checking in scenarios
> > > where the input value overflows the intended output variable.
> > > This results in this function successfully returning, even when the
> > > output does not match the input string (aka the function returns
> > > successfully even when the result is wrong).
> > >
> > > Or as it was mentioned [1], "...simple_strtol(), simple_strtoll(),
> > > simple_strtoul(), and simple_strtoull() functions explicitly ignore
> > > overflows, which may lead to unexpected results in callers."
> > > Hence, the use of those functions is discouraged.
> > >
> > > This patch replaces all uses of the simple_strtoul with the safer
> > > alternatives kstrtoint and kstrtol.
> > >
> > > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#simple-strtol-simple-strtoll-simple-strtoul-simple-strtoull
> > >
> > > Signed-off-by: Yuran Pereira <yuran.pereira@...mail.com>
> > > ---
> > >  kernel/trace/trace_kdb.c | 14 ++++++--------
> > >  1 file changed, 6 insertions(+), 8 deletions(-)
> > >
> > > diff --git a/kernel/trace/trace_kdb.c b/kernel/trace/trace_kdb.c
> > > index 59857a1ee44c..3891f885e4a6 100644
> > > --- a/kernel/trace/trace_kdb.c
> > > +++ b/kernel/trace/trace_kdb.c
> > > @@ -96,23 +96,21 @@ static int kdb_ftdump(int argc, const char **argv)
> > >  {
> > >         int skip_entries = 0;
> > >         long cpu_file;
> > > -       char *cp;
> > > +       int err;
> > >         int cnt;
> > >         int cpu;
> > >
> > >         if (argc > 2)
> > >                 return KDB_ARGCOUNT;
> > >
> > > -       if (argc) {
> > > -               skip_entries = simple_strtol(argv[1], &cp, 0);
> > > -               if (*cp)
> > > +       if (argc)
> > > +               if (kstrtoint(argv[1], 0, &skip_entries))
> > >                         skip_entries = 0;
> > > -       }
> >
> > Similar nit about braces as in patch #1. tl;dr is change the above to:
> >
> > if (argc && kstrtoint(argv[1], 0, &skip_entries))
> >   skip_entries = 0;
>
> Surely that should be:
>
> if (...)
>         return KDB_BADINT;
>
> There seems little point switching to a "safer" API if we just ignore the
> errors it provides us.

Ah, sure. I have no objections to that. Note that would have also been
possible with the old code, which did still do awkward error checking,
so I assumed that it was a conscious decision. ...but I'm definitely
happier with the error being reported instead of glossed over.

-Doug