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

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Date:   Wed, 31 Jul 2019 09:58:30 +0000
From:   Yoshihiro Shimoda <yoshihiro.shimoda.uh@...esas.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
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 Geert-san,

> From: Geert Uytterhoeven, Sent: Wednesday, July 31, 2019 6:27 PM
> 
> Hi Shimoda-san,
> 
> 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.

> 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.

Best regards,
Yoshihiro Shimoda

> 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