linux-kernel - Re: [PATCH] phy: renesas: rcar-gen3-usb2: Fix sysfs interface of "role"

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Date:   Wed, 31 Jul 2019 12:09:48 +0200
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
Cc:     Kishon Vijay Abraham I <kishon@...com>,
        Pavel Machek <pavel@...x.de>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH] phy: renesas: rcar-gen3-usb2: Fix sysfs interface of "role"

Hi Shimoda-san,

On Wed, Jul 31, 2019 at 11:58 AM Yoshihiro Shimoda
<yoshihiro.shimoda.uh@...esas.com> wrote:
> > From: Geert Uytterhoeven, Sent: Wednesday, July 31, 2019 6:27 PM
> > On Wed, Jul 31, 2019 at 11:04 AM Yoshihiro Shimoda
> > <yoshihiro.shimoda.uh@...esas.com> wrote:
> > > Since the role_store() uses strncmp(), it's possible to refer
> > > out-of-memory if the sysfs data size is smaller than strlen("host").
> > > This patch fixes it by using sysfs_streq() instead of strncmp().
> > >
> > > Reported-by: Pavel Machek <pavel@...x.de>
> > > Fixes: 9bb86777fb71 ("phy: rcar-gen3-usb2: add sysfs for usb role swap")
> > > Cc: <stable@...r.kernel.org> # v4.10+
> > > Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
> >
> > Reviewed-by: Geert Uytterhoeven <geert+renesas@...der.be>
>
> Thank you for your review!
>
> > > ---
> > >  Just a record. The role_store() doesn't need to check the count because
> > >  the sysfs_streq() checks the first argument is NULL or not.
> >
> > Is that wat you mean? sysfs_streq() doesn't seem to check for NULL pointers.
>
> Oops, sorry for unclear. I meant a NULL-terminated string, not NULL pointer.

OK.

> > Isn't the real reason that sysfs (kernfs) guarantees that the passed buffer
> > is NUL-terminated?
>
> I doesn't check in detail, but I assume so.

I have checked that recently, so it is OK.

Gr{oetje,eeting}s,

                        Geert

-- 
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds