From: Alan Stern <stern@rowland.harvard.edu>
To: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Kees Cook <keescook@chromium.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Arnd Bergmann <arnd@arndb.de>, Al Cooper <alcooperx@gmail.com>,
linux-usb@vger.kernel.org,
Florian Fainelli <f.fainelli@gmail.com>,
linux-kernel@vger.kernel.org,
bcm-kernel-feedback-list@broadcom.com,
linux-hardening@vger.kernel.org
Subject: Re: [PATCH 1/2] USB: EHCI: Add register array bounds to HCS ports
Date: Wed, 18 Aug 2021 11:02:27 -0400 [thread overview]
Message-ID: <20210818150227.GE193695@rowland.harvard.edu> (raw)
In-Reply-To: <CAHp75VdE3akTqmJ6VE4+Q4F959JscvZpiJok4=2JmjDjubtuxw@mail.gmail.com>
On Wed, Aug 18, 2021 at 12:48:17PM +0300, Andy Shevchenko wrote:
> On Wed, Aug 18, 2021 at 7:30 AM Kees Cook <keescook@chromium.org> wrote:
> >
> > The original EHCI register struct used a trailing 0-element array for
> > addressing the N_PORTS-many available registers. However, after
> > commit a46af4ebf9ff ("USB: EHCI: define extension registers like normal ones")
> > the 0-element array started to overlap the USBMODE extension register.
> >
> > To avoid future compile-time warnings about accessing indexes within a
> > 0-element array, rearrange the struct to actually describe the expected
> > layout (max 15 registers) with a union. All offsets remain the same, and
> > bounds checking becomes possible on accesses to port_status and hostpc.
>
> ...
>
> > /* HOSTPC: offset 0x84 */
> > - u32 hostpc[0]; /* HOSTPC extension */
> > + u32 hostpc[HCS_N_PORTS_MAX];
> > #define HOSTPC_PHCD (1<<22) /* Phy clock disable */
> > #define HOSTPC_PSPD (3<<25) /* Port speed detection */
> >
> > - u32 reserved5[17];
> > + u32 reserved5[2];
>
> Shouldn't it be rather [17 - PORT_MAX]? for accuracy?
> Or also a union approach?
It's okay to use [2] here. The only purpose is to ensure that the
following usbmode_ex field is allocated at offset 0xc8; there's no
special intrinsic meaning to that 17 value.
Alan Stern
next prev parent reply other threads:[~2021-08-18 15:02 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-18 4:30 [PATCH 0/2] USB: EHCI: Add register array bounds to HCS ports Kees Cook
2021-08-18 4:30 ` [PATCH 1/2] " Kees Cook
2021-08-18 9:48 ` Andy Shevchenko
2021-08-18 15:02 ` Alan Stern [this message]
2021-08-18 14:44 ` Alan Stern
2021-08-18 17:17 ` Kees Cook
2021-08-18 4:30 ` [PATCH 2/2] USB: EHCI: Add alias for Broadcom INSNREG Kees Cook
2021-08-18 14:57 ` Alan Stern
2021-08-18 17:15 ` Kees Cook
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