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

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Message-ID: <20231206113753.GB81045@aspen.lan>
Date:   Wed, 6 Dec 2023 11:37:53 +0000
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Doug Anderson <dianders@...omium.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

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.


Daniel.