linux-kernel - Re: [PATCH v1] at24: fix memory corruption race condition

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Message-ID: <CAMRc=Mcbi8BQ-tHNs+BVjbm3aDSVY0zzOM4QfND3d2y8ryT62g@mail.gmail.com>
Date: Thu, 18 Apr 2024 01:59:46 +0200
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Daniel Okazaki <dtokazaki@...gle.com>
Cc: Arnd Bergmann <arnd@...db.de>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, kernel-team@...roid.com, 
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1] at24: fix memory corruption race condition

On Thu, Apr 18, 2024 at 1:07 AM Daniel Okazaki <dtokazaki@...gle.com> wrote:
>
> If the eeprom is not accessible, an nvmem device will be registered, the
> read will fail, and the device will be torn down. If another driver
> accesses the nvmem device after the teardown, it will reference
> invalid memory.
>
> Move the failure point before registering the nvmem device.
>
> Signed-off-by: Daniel Okazaki <dtokazaki@...gle.com>
> ---
>  drivers/misc/eeprom/at24.c | 18 +++++++++---------
>  1 file changed, 9 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/misc/eeprom/at24.c b/drivers/misc/eeprom/at24.c
> index 572333ead5fb..4bd4f32bcdab 100644
> --- a/drivers/misc/eeprom/at24.c
> +++ b/drivers/misc/eeprom/at24.c
> @@ -758,15 +758,6 @@ static int at24_probe(struct i2c_client *client)
>         }
>         pm_runtime_enable(dev);
>
> -       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> -       if (IS_ERR(at24->nvmem)) {
> -               pm_runtime_disable(dev);
> -               if (!pm_runtime_status_suspended(dev))
> -                       regulator_disable(at24->vcc_reg);
> -               return dev_err_probe(dev, PTR_ERR(at24->nvmem),
> -                                    "failed to register nvmem\n");
> -       }
> -
>         /*
>          * Perform a one-byte test read to verify that the chip is functional,
>          * unless powering on the device is to be avoided during probe (ie.
> @@ -782,6 +773,15 @@ static int at24_probe(struct i2c_client *client)
>                 }
>         }
>
> +       at24->nvmem = devm_nvmem_register(dev, &nvmem_config);
> +       if (IS_ERR(at24->nvmem)) {
> +               pm_runtime_disable(dev);
> +               if (!pm_runtime_status_suspended(dev))
> +                       regulator_disable(at24->vcc_reg);
> +               return dev_err_probe(dev, PTR_ERR(at24->nvmem),
> +                                    "failed to register nvmem\n");
> +       }
> +
>         /* If this a SPD EEPROM, probe for DDR3 thermal sensor */
>         if (cdata == &at24_data_spd)
>                 at24_probe_temp_sensor(client);
> --
> 2.44.0.683.g7961c838ac-goog
>

Looks good, can you add a Fixes tag?

Thanks,
Bartosz