linux-kernel - Re: [PATCH] driver: of: Properly truncate command line if too long

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Message-ID: <CAL_JsqLeA2va05A78M893rAGoeMr-CztdiZouq-PSDFfsJ_-EA@mail.gmail.com>
Date:   Tue, 6 Apr 2021 08:40:46 -0500
From:   Rob Herring <robh+dt@...nel.org>
To:     Alex Ghiti <alex@...ti.fr>
Cc:     Frank Rowand <frowand.list@...il.com>,
        Dmitry Vyukov <dvyukov@...gle.com>, devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] driver: of: Properly truncate command line if too long

On Sat, Apr 3, 2021 at 7:09 AM Alex Ghiti <alex@...ti.fr> wrote:
>
> Hi,
>
> Le 3/16/21 à 3:38 PM, Alexandre Ghiti a écrit :
> > In case the command line given by the user is too long, warn about it
> > and truncate it to the last full argument.
> >
> > This is what efi already does in commit 80b1bfe1cb2f ("efi/libstub:
> > Don't parse overlong command lines").
> >
> > Reported-by: Dmitry Vyukov <dvyukov@...gle.com>
> > Signed-off-by: Alexandre Ghiti <alex@...ti.fr>
> > ---
> >   drivers/of/fdt.c | 21 ++++++++++++++++++++-
> >   1 file changed, 20 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/of/fdt.c b/drivers/of/fdt.c
> > index dcc1dd96911a..de4c6f9bac39 100644
> > --- a/drivers/of/fdt.c
> > +++ b/drivers/of/fdt.c
> > @@ -25,6 +25,7 @@
> >   #include <linux/serial_core.h>
> >   #include <linux/sysfs.h>
> >   #include <linux/random.h>
> > +#include <linux/ctype.h>
> >
> >   #include <asm/setup.h>  /* for COMMAND_LINE_SIZE */
> >   #include <asm/page.h>
> > @@ -1050,9 +1051,27 @@ int __init early_init_dt_scan_chosen(unsigned long node, const char *uname,
> >
> >       /* Retrieve command line */
> >       p = of_get_flat_dt_prop(node, "bootargs", &l);
> > -     if (p != NULL && l > 0)
> > +     if (p != NULL && l > 0) {
> >               strlcpy(data, p, min(l, COMMAND_LINE_SIZE));
> >
> > +             /*
> > +              * If the given command line size is larger than
> > +              * COMMAND_LINE_SIZE, truncate it to the last complete
> > +              * parameter.
> > +              */
> > +             if (l > COMMAND_LINE_SIZE) {
> > +                     char *cmd_p = (char *)data + COMMAND_LINE_SIZE - 1;
> > +
> > +                     while (!isspace(*cmd_p))
> > +                             cmd_p--;
> > +
> > +                     *cmd_p = '\0';
> > +
> > +                     pr_err("Command line is too long: truncated to %d bytes\n",
> > +                            (int)(cmd_p - (char *)data + 1));
> > +             }
> > +     }
> > +
> >       /*
> >        * CONFIG_CMDLINE is meant to be a default in case nothing else
> >        * managed to set the command line, unless CONFIG_CMDLINE_FORCE
> >
>
> Any thought about that ?

It looks fine to me, but this will need to be adapted to the generic
command line support[1][2] when that is merged. So I've been waiting
to see if that's going to happen this cycle.

Rob

[1] https://lore.kernel.org/lkml/cover.1616765869.git.christophe.leroy@csgroup.eu/
[2] https://lore.kernel.org/lkml/41021d66db2ab427c14255d2a24bb4517c8b58fd.1617126961.git.danielwa@cisco.com/