linux-kernel - Re: [PATCH] iio: dac: ad3552r-hs: fix out-of-bound write in ad3552r_hs_write_data

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Message-ID: <42e7a6644812626d7c1a58eb51bc7418ff31c0c4.camel@gmail.com>
Date: Mon, 27 Oct 2025 16:05:11 +0000
From: Nuno Sá <noname.nuno@...il.com>
To: Miaoqian Lin <linmq006@...il.com>, Lars-Peter Clausen <lars@...afoo.de>,
  Michael Hennerich <Michael.Hennerich@...log.com>, Jonathan Cameron
 <jic23@...nel.org>, David Lechner	 <dlechner@...libre.com>, Nuno
 Sá <nuno.sa@...log.com>,  Andy Shevchenko	
 <andy@...nel.org>, Angelo Dureghello <adureghello@...libre.com>, 
	linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: stable@...r.kernel.org
Subject: Re: [PATCH] iio: dac: ad3552r-hs: fix out-of-bound write in
 ad3552r_hs_write_data_source

On Mon, 2025-10-27 at 23:07 +0800, Miaoqian Lin wrote:
> When simple_write_to_buffer() succeeds, it returns the number of bytes
> actually copied to the buffer, which may be less than the requested
> 'count' if the buffer size is insufficient. However, the current code
> incorrectly uses 'count' as the index for null termination instead of
> the actual bytes copied, leading to out-of-bound write.
> 
> Add a check for the count and use the return value as the index.
> 
> Found via static analysis. This is similar to the
> commit da9374819eb3 ("iio: backend: fix out-of-bound write")
> 
> Fixes: b1c5d68ea66e ("iio: dac: ad3552r-hs: add support for internal ramp")
> Cc: stable@...r.kernel.org
> Signed-off-by: Miaoqian Lin <linmq006@...il.com>
> ---

Reviewed-by: Nuno Sá <nuno.sa@...log.com>

>  drivers/iio/dac/ad3552r-hs.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/dac/ad3552r-hs.c b/drivers/iio/dac/ad3552r-hs.c
> index 41b96b48ba98..a9578afa7015 100644
> --- a/drivers/iio/dac/ad3552r-hs.c
> +++ b/drivers/iio/dac/ad3552r-hs.c
> @@ -549,12 +549,15 @@ static ssize_t ad3552r_hs_write_data_source(struct file
> *f,
>  
>  	guard(mutex)(&st->lock);
>  
> +	if (count >= sizeof(buf))
> +		return -ENOSPC;
> +
>  	ret = simple_write_to_buffer(buf, sizeof(buf) - 1, ppos, userbuf,
>  				     count);
>  	if (ret < 0)
>  		return ret;
>  
> -	buf[count] = '\0';
> +	buf[ret] = '\0';
>  
>  	ret = match_string(dbgfs_attr_source, ARRAY_SIZE(dbgfs_attr_source),
>  			   buf);