staging: comedi: dmm32at: Fix endian problem for AI command data

BugLink: https://bugs.launchpad.net/bugs/1919492
commit 54999c0d94b3c26625f896f8e3460bc029821578 upstream.

The analog input subdevice supports Comedi asynchronous commands that
use Comedi's 16-bit sample format.  However, the call to
`comedi_buf_write_samples()` is passing the address of a 32-bit integer
variable.  On bigendian machines, this will copy 2 bytes from the wrong
end of the 32-bit value.  Fix it by changing the type of the variable
holding the sample value to `unsigned short`.

[Note: the bug was introduced in commit 1700529b24cc ("staging: comedi:
dmm32at: use comedi_buf_write_samples()") but the patch applies better
to the later (but in the same kernel release) commit 0c0eadadcbe6e
("staging: comedi: dmm32at: introduce dmm32_ai_get_sample()").]

Fixes: 0c0eadadcbe6e ("staging: comedi: dmm32at: introduce dmm32_ai_get_sample()")
Cc: <stable@vger.kernel.org> # 3.19+
Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
Link: https://lore.kernel.org/r/20210223143055.257402-7-abbotti@mev.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

diff --git a/drivers/staging/comedi/drivers/dmm32at.c b/drivers/staging/comedi/drivers/dmm32at.c
index 17e6018918bbf9bc51359f5214756c1adf36cd0d..56682f01242fd024c9900db9a23003e698ee1d85 100644 (file)
--- a/drivers/staging/comedi/drivers/dmm32at.c
+++ b/drivers/staging/comedi/drivers/dmm32at.c
@@ -404,7 +404,7 @@ static irqreturn_t dmm32at_isr(int irq, void *d)
 {
        struct comedi_device *dev = d;
        unsigned char intstat;
-       unsigned int val;
+       unsigned short val;
        int i;
 
        if (!dev->attached) {