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From:   Andy Shevchenko <andy.shevchenko@gmail.com>
Date:   Sun, 5 Sep 2021 19:13:54 +0300
Message-ID: <CAHp75VcqTf3qef76nAE_TN32MdcvtYxZP2O8Oekap-_34mey0A@mail.gmail.com>
Subject: Re: [PATCH] serial: 8250_pci: Prefer struct_size over open coded arithmetic
To:     Len Baker <len.baker@gmx.com>
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jiri Slaby <jirislaby@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        "Maciej W. Rozycki" <macro@orcam.me.uk>,
        Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
        Mario Kleiner <mario.kleiner.de@gmail.com>,
        Geert Uytterhoeven <geert+renesas@glider.be>,
        Randy Wright <rwright@hpe.com>,
        Christian Gmeiner <christian.gmeiner@gmail.com>,
        Tobias Diedrich <tobiasdiedrich@gmail.com>,
        YueHaibing <yuehaibing@huawei.com>,
        "open list:SERIAL DRIVERS" <linux-serial@vger.kernel.org>,
        linux-hardening@vger.kernel.org,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Sun, Sep 5, 2021 at 6:58 PM Len Baker <len.baker@gmx.com> wrote:
>
> As noted in the "Deprecated Interfaces, Language Features, Attributes,
> and Conventions" documentation [1], size calculations (especially
> multiplication) should not be performed in memory allocator (or similar)
> function arguments due to the risk of them overflowing. This could lead
> to values wrapping around and a smaller allocation being made than the
> caller was expecting. Using those allocations could lead to linear
> overflows of heap memory and other misbehaviors.
>
> So, use the struct_size() helper to do the arithmetic instead of the
> argument "size + size * count" in the kzalloc() function.

Makes sense
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

> [1] https://www.kernel.org/doc/html/v5.14/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments
>
> Signed-off-by: Len Baker <len.baker@gmx.com>
> ---
>  drivers/tty/serial/8250/8250_pci.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
>
> diff --git a/drivers/tty/serial/8250/8250_pci.c b/drivers/tty/serial/8250/8250_pci.c
> index a808c283883e..b97ade35d4a3 100644
> --- a/drivers/tty/serial/8250/8250_pci.c
> +++ b/drivers/tty/serial/8250/8250_pci.c
> @@ -3981,9 +3981,7 @@ pciserial_init_ports(struct pci_dev *dev, const struct pciserial_board *board)
>                         nr_ports = rc;
>         }
>
> -       priv = kzalloc(sizeof(struct serial_private) +
> -                      sizeof(unsigned int) * nr_ports,
> -                      GFP_KERNEL);
> +       priv = kzalloc(struct_size(priv, line, nr_ports), GFP_KERNEL);
>         if (!priv) {
>                 priv = ERR_PTR(-ENOMEM);
>                 goto err_deinit;
> --
> 2.25.1
>


-- 
With Best Regards,
Andy Shevchenko