Re: [PATCH] iio: magnetometer: ak8975: fix potential kernel stack memory leak

[Andy Shevchenko <andriy.shevchenko@intel.com>]

On Thu, May 14, 2026 at 01:38:17PM +0200, Joshua Crofts via B4 Relay wrote:

> Currently in the AK8975 driver there are two instances where potential
> uninitialized kernel stack memory leaks can occur. If
> i2c_smbus_read_i2c_block_data_or_emulated() returns a value less than
> the size of the buffer, uninitialized bytes are retained in the buffer
> and later the buffer is passed on to IIO buffers, potentially leaking
> memory to userspace.
> 
> Fix this by adding checks whether the return value of the function is
> equal to the size of the buffer and subsequently if the value is
> lesser than zero to distinguish from a returned error code.

...

> -	if (ret < 0)
> +	if (ret != sizeof(rval)) {
> +		if (ret >= 0)
> +			ret = -EIO;
>  		goto exit;
> +	}

Still better to not mix the two

	if (ret < 0)
		goto exit;
	if (ret != sizeof(rval)) {
		ret = -EIO;
		goto exit;
	}

...

Ditto for the second case.

-- 
With Best Regards,
Andy Shevchenko