[PATCH] staging: axis-fifo: fix integer underflow in tx_fifo_depth

[Vladan Kalaba <vladan.kalaba@gmail.com>]

Fix integer underflow if tx_fifo_depth < 4 in axis-fifo.c due
to check in axis_fifo_write() subtracting 4.

Fixes: 52ff2b840bc7 ("staging: axis-fifo: fix maximum TX packet length check")
Cc: stable@vger.kernel.org
Signed-off-by: Vladan Kalaba <vladan.kalaba@gmail.com>
---
 drivers/staging/axis-fifo/axis-fifo.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/staging/axis-fifo/axis-fifo.c b/drivers/staging/axis-fifo/axis-fifo.c
index 7bb35e11d1dd..066124122caa 100644
--- a/drivers/staging/axis-fifo/axis-fifo.c
+++ b/drivers/staging/axis-fifo/axis-fifo.c
@@ -413,6 +413,11 @@ static int axis_fifo_parse_dt(struct axis_fifo *fifo)
 	if (ret)
 		return ret;
 
+	if (fifo->tx_fifo_depth < 4) {
+		dev_err(fifo->dt_device, "tx_fifo_depth must be >= 4\n");
+		return -EINVAL;
+	}
+
 	ret = of_property_read_u32(node, "xlnx,use-rx-data",
 				   &fifo->has_rx_fifo);
 	if (ret)
-- 
2.53.0