linux-kernel - Re: [PATCH AUTOSEL 4.14 19/60] iio:core: Fix bug in length of event info_mask and catch unhandled bits set in masks.

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Date:   Sun, 21 Jul 2019 18:27:02 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Young Xiao <92siuyang@...il.com>,
        Alexandru Ardelean <alexandru.ardelean@...log.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        linux-iio@...r.kernel.org
Subject: Re: [PATCH AUTOSEL 4.14 19/60] iio:core: Fix bug in length of event
 info_mask and catch unhandled bits set in masks.

On Fri, 19 Jul 2019 00:10:28 -0400
Sasha Levin <sashal@...nel.org> wrote:

> From: Young Xiao <92siuyang@...il.com>
> 
> [ Upstream commit 936d3e536dcf88ce80d27bdb637009b13dba6d8c ]
> 
> The incorrect limit for the for_each_set_bit loop was noticed whilst fixing
> this other case.  Note that as we only have 3 possible entries a the moment
> and the value was set to 4, the bug would not have any effect currently.
> It will bite fairly soon though, so best fix it now.
> 
> See commit ef4b4856593f ("iio:core: Fix bug in length of event info_mask and
> catch unhandled bits set in masks.") for details.
> 
> Signed-off-by: Young Xiao <92siuyang@...il.com>
> Reviewed-by: Alexandru Ardelean <alexandru.ardelean@...log.com>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Signed-off-by: Sasha Levin <sashal@...nel.org>

As the patch states, this bug doesn't have any impact.  It would only
be triggered by a buggy driver setting a bit in that mask that makes no
sense.

So it's good to fix in upstream, but debatable if it's worth porting back
to stable.

I don't have a strong opinion on this one and again, it should do no
harm.

Jonathan

> ---
>  drivers/iio/industrialio-core.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index 97b7266ee0ff..b0f952984983 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -1116,6 +1116,8 @@ static int iio_device_add_info_mask_type_avail(struct iio_dev *indio_dev,
>  	char *avail_postfix;
>  
>  	for_each_set_bit(i, infomask, sizeof(*infomask) * 8) {
> +		if (i >= ARRAY_SIZE(iio_chan_info_postfix))
> +			return -EINVAL;
>  		avail_postfix = kasprintf(GFP_KERNEL,
>  					  "%s_available",
>  					  iio_chan_info_postfix[i]);