linux-kernel - Re: [PATCH][next] gpio: xilinx: Fix potential integer overflow on shift of a u32 int

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Message-ID: <CAHp75VdJ9n6Sm2HQYE_bfg-5vXceA3aG5aXOfCctxDjzhLVXpA@mail.gmail.com>
Date:   Mon, 17 May 2021 10:04:59 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     David Laight <David.Laight@...lab.com>
Cc:     Colin King <colin.king@...onical.com>,
        Shubhrajyoti Datta <shubhrajyoti.datta@...inx.com>,
        Srinivas Neeli <srinivas.neeli@...inx.com>,
        Michal Simek <michal.simek@...inx.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        "linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH][next] gpio: xilinx: Fix potential integer overflow on
 shift of a u32 int

On Thu, May 13, 2021 at 1:04 PM David Laight <David.Laight@...lab.com> wrote:
> > From: Colin Ian King <colin.king@...onical.com>

> > @@ -99,7 +99,7 @@ static inline void xgpio_set_value32(unsigned long *map, int bit, u32 v)
> >       const unsigned long offset = (bit % BITS_PER_LONG) & BIT(5);
> >
> >       map[index] &= ~(0xFFFFFFFFul << offset);
> > -     map[index] |= v << offset;
> > +     map[index] |= (unsigned long)v << offset;
> >  }
>
> That code looks dubious on 32bit architectures.
>
> I don't have 02b3f84d9080 in any of my source trees.

Can you please be more specific on which code is dubious on 32-bit
arches and why?

> But that patch may itself be very dubious.
>
> Since the hardware requires explicit bits be set, relying
> on the bitmap functions seems pointless and possibly wrong.
> Clearly they cause additional problems because they use long[]
> and here the code needs u32[].

-- 
With Best Regards,
Andy Shevchenko