[PATCH] [RFC] iio: pressure: dlhl60d: Check mask_width for IRQs

[Kees Cook]

Clang tripped over a FORTIFY warning in this code, and while it seems it
may be a false positive in Clang due to loop unwinding, the code in
question seems to make a lot of assumptions. Comments added, and the
Clang warning[1] has been worked around by growing the array size.
Also there was an uninitialized 4th byte in the __be32 array that was
being sent through to iio_push_to_buffers().

Link: https://github.com/ClangBuiltLinux/linux/issues/2000 [1]
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
Cc: Jonathan Cameron <jic23@xxxxxxxxxx>
Cc: Lars-Peter Clausen <lars@xxxxxxxxxx>
Cc: "Uwe Kleine-König" <u.kleine-koenig@xxxxxxxxxxxxxx>
Cc: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Cc: "Nuno Sá" <nuno.sa@xxxxxxxxxx>
Cc: linux-iio@xxxxxxxxxxxxxxx
---
 drivers/iio/pressure/dlhl60d.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/pressure/dlhl60d.c b/drivers/iio/pressure/dlhl60d.c
index 28c8269ba65d..9bbecd0bfe88 100644
--- a/drivers/iio/pressure/dlhl60d.c
+++ b/drivers/iio/pressure/dlhl60d.c
@@ -250,20 +250,27 @@ static irqreturn_t dlh_trigger_handler(int irq, void *private)
 	struct dlh_state *st = iio_priv(indio_dev);
 	int ret;
 	unsigned int chn, i = 0;
-	__be32 tmp_buf[2];
+	/* This was only an array pair of 4 bytes. */
+	__be32 tmp_buf[4] = { };
 
 	ret = dlh_start_capture_and_read(st);
 	if (ret)
 		goto out;
 
+	/* Nothing was checking masklength vs ARRAY_SIZE(tmp_buf)? */
+	if (WARN_ON_ONCE(indio_dev->masklength > ARRAY_SIZE(tmp_buf)))
+		goto out;
+
 	for_each_set_bit(chn, indio_dev->active_scan_mask,
 		indio_dev->masklength) {
-		memcpy(tmp_buf + i,
+		/* This is copying 3 bytes. What about the 4th? */
+		memcpy(&tmp_buf[i],
 			&st->rx_buf[1] + chn * DLH_NUM_DATA_BYTES,
 			DLH_NUM_DATA_BYTES);
 		i++;
 	}
 
+	/* How do we know the iio buffer_list has only 2 items? */
 	iio_push_to_buffers(indio_dev, tmp_buf);
 
 out:
-- 
2.34.1