linux-kernel - Re: [PATCH v2] iio: multiplexer: fix unsigned check with less than zero

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Message-ID: <d91161d3-3795-af99-16ba-31de49cc42a4@kernel.org>
Date:   Sat, 11 Mar 2017 18:30:36 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Peter Rosin <peda@...ntia.se>,
        Colin Ian King <colin.king@...onical.com>
Cc:     Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-iio@...r.kernel.org, kernel-janitors@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] iio: multiplexer: fix unsigned check with less than
 zero

On 08/03/17 13:28, Peter Rosin wrote:
> Comparing a size_t with less than zero is always false as size_t
> is unsigned. So, change the type of the variable to ssize_t and
> replicate the size check from mux_configure_channel() into
> mux_write_ext_info() thus ensuring that the size will fit in the
> ssize_t variable.
> 
> Detected by CoverityScan, CID#1415278 ("Unsigned compared against 0")
> 
> Reported-by: Colin Ian King <colin.king@...onical.com>
> Signed-off-by: Peter Rosin <peda@...ntia.se>
For what it's worth, looks good to me.

Jonathan
> ---
>  drivers/iio/multiplexer/iio-mux.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> Hi!
> 
> Here's what intend to queue up.
> 
> Cheers,
> peda
> 
> diff --git a/drivers/iio/multiplexer/iio-mux.c b/drivers/iio/multiplexer/iio-mux.c
> index 94d40f9b..bab9e69 100644
> --- a/drivers/iio/multiplexer/iio-mux.c
> +++ b/drivers/iio/multiplexer/iio-mux.c
> @@ -21,7 +21,7 @@
>  
>  struct mux_ext_info_cache {
>  	char *data;
> -	size_t size;
> +	ssize_t size;
>  };
>  
>  struct mux_child {
> @@ -206,6 +206,9 @@ static ssize_t mux_write_ext_info(struct iio_dev *indio_dev, uintptr_t private,
>  	char *new;
>  	ssize_t ret;
>  
> +	if (len >= PAGE_SIZE)
> +		return -EINVAL;
> +
>  	ret = iio_mux_select(mux, idx);
>  	if (ret < 0)
>  		return ret;
>