linux-kernel - Re: [PATCH] staging: greybus: spilib: fix use-after-free after deregistration

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Message-ID: <m3lgjtdf28.fsf@gmail.com>
Date:   Sun, 29 Oct 2017 17:44:31 +0000
From:   Rui Miguel Silva <rmfrfs@...il.com>
To:     Johan Hovold <johan@...nel.org>
Cc:     Rui Miguel Silva <rmfrfs@...il.com>,
        Viresh Kumar <vireshk@...nel.org>,
        Alex Elder <elder@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        greybus-dev@...ts.linaro.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, stable <stable@...r.kernel.org>
Subject: Re: [PATCH] staging: greybus: spilib: fix use-after-free after deregistration

Hi Johan,
Thanks for the patch.

On Sun 29 Oct 2017 at 12:01, Johan Hovold <johan@...nel.org> wrote:
> Remove erroneous spi_master_put() after controller deregistration which
> would access the already freed spi controller.
>
> Note that spi_unregister_master() drops our only controller reference.
>
> Fixes: ba3e67001b42 ("greybus: SPI: convert to a gpbridge driver")
> Cc: stable <stable@...r.kernel.org>     # 4.9
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Signed-off-by: Johan Hovold <johan@...nel.org>

Reviewed-by: Rui Miguel Silva <rmfrfs@...il.com>

---
Cheers,
	Rui

> ---
>  drivers/staging/greybus/spilib.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/staging/greybus/spilib.c b/drivers/staging/greybus/spilib.c
> index e97b19148497..1e7321a1404c 100644
> --- a/drivers/staging/greybus/spilib.c
> +++ b/drivers/staging/greybus/spilib.c
> @@ -544,11 +544,14 @@ int gb_spilib_master_init(struct gb_connection *connection, struct device *dev,
>  
>  	return 0;
>  
> -exit_spi_unregister:
> -	spi_unregister_master(master);
>  exit_spi_put:
>  	spi_master_put(master);
>  
> +	return ret;
> +
> +exit_spi_unregister:
> +	spi_unregister_master(master);
> +
>  	return ret;
>  }
>  EXPORT_SYMBOL_GPL(gb_spilib_master_init);
> @@ -558,7 +561,6 @@ void gb_spilib_master_exit(struct gb_connection *connection)
>  	struct spi_master *master = gb_connection_get_data(connection);
>  
>  	spi_unregister_master(master);
> -	spi_master_put(master);
>  }
>  EXPORT_SYMBOL_GPL(gb_spilib_master_exit);