linux-kernel - Re: [PATCH v10 3/7] i2c: fsi: Add port structures

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Date:   Wed, 20 Jun 2018 13:29:04 +0930
From:   Joel Stanley <joel@....id.au>
To:     Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:     Eddie James <eajames@...ux.vnet.ibm.com>,
        linux-i2c@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Wolfram Sang <wsa@...-dreams.de>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Randy Dunlap <rdunlap@...radead.org>,
        Andy Shevchenko <andy.shevchenko@...il.com>,
        Peter Rosin <peda@...ntia.se>
Subject: Re: [PATCH v10 3/7] i2c: fsi: Add port structures

On 20 June 2018 at 13:04, Benjamin Herrenschmidt
<benh@...nel.crashing.org> wrote:
> On Wed, 2018-06-13 at 14:36 -0500, Eddie James wrote:
>>  }
>>
>> +static int fsi_i2c_remove(struct device *dev)
>> +{
>> +       struct fsi_i2c_master *i2c = dev_get_drvdata(dev);
>> +       struct fsi_i2c_port *port;
>> +
>> +       list_for_each_entry(port, &i2c->ports, list) {
>> +               i2c_del_adapter(&port->adapter);
>> +               kfree(port);
>> +       }
>> +
>> +       return 0;
>> +}
>> +
>
> This is a use-after-free, the list linkage of the freed port is used to
> get to the next one. With memory poisoning, kbooom !
>
> You can fold that in:
>
> From f9d9092160897e7308f6990067a03e937339537f Mon Sep 17 00:00:00 2001
> From: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> Date: Wed, 20 Jun 2018 13:27:32 +1000
> Subject: [PATCH] i2c: fsi: Fix use after free

This fixes the issue I was seeing. For the series:

Tested-by: Joel Stanley <joel@....id.au>

Thanks,

Joel


>
> Signed-off-by: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> ---
>  drivers/i2c/busses/i2c-fsi.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-fsi.c b/drivers/i2c/busses/i2c-fsi.c
> index 713959b44403..ff69ab6aa79a 100644
> --- a/drivers/i2c/busses/i2c-fsi.c
> +++ b/drivers/i2c/busses/i2c-fsi.c
> @@ -696,9 +696,10 @@ static int fsi_i2c_probe(struct device *dev)
>  static int fsi_i2c_remove(struct device *dev)
>  {
>         struct fsi_i2c_master *i2c = dev_get_drvdata(dev);
> -       struct fsi_i2c_port *port;
> +       struct fsi_i2c_port *port, *tmp;
>
> -       list_for_each_entry(port, &i2c->ports, list) {
> +       list_for_each_entry_safe(port,tmp, &i2c->ports, list) {
> +               list_del(&port->list);
>                 i2c_del_adapter(&port->adapter);
>                 kfree(port);
>         }
>