[PATCH 5.10 005/131] spi: spi-zynq-qspi: Fix stack violation bug

[Greg Kroah-Hartman]

From: Karen Dombroski <karen.dombroski@xxxxxxxxxxxxxxxxxx>

[ Upstream commit 6d5ff8e632a4f2389c331e5554cd1c2a9a28c7aa ]

When the number of bytes for the op is greater than one, the read could
run off the end of the function stack and cause a crash.

This patch restores the behaviour of safely reading out of the original
opcode location.

Signed-off-by: Karen Dombroski <karen.dombroski@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20210429053802.17650-3-amit.kumar-mahapatra@xxxxxxxxxx
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 drivers/spi/spi-zynq-qspi.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/spi/spi-zynq-qspi.c b/drivers/spi/spi-zynq-qspi.c
index 5d8a5ee62fa2..2765289028fa 100644
--- a/drivers/spi/spi-zynq-qspi.c
+++ b/drivers/spi/spi-zynq-qspi.c
@@ -528,18 +528,17 @@ static int zynq_qspi_exec_mem_op(struct spi_mem *mem,
 	struct zynq_qspi *xqspi = spi_controller_get_devdata(mem->spi->master);
 	int err = 0, i;
 	u8 *tmpbuf;
-	u8 opcode = op->cmd.opcode;
 
 	dev_dbg(xqspi->dev, "cmd:%#x mode:%d.%d.%d.%d\n",
-		opcode, op->cmd.buswidth, op->addr.buswidth,
+		op->cmd.opcode, op->cmd.buswidth, op->addr.buswidth,
 		op->dummy.buswidth, op->data.buswidth);
 
 	zynq_qspi_chipselect(mem->spi, true);
 	zynq_qspi_config_op(xqspi, mem->spi);
 
-	if (op->cmd.nbytes) {
+	if (op->cmd.opcode) {
 		reinit_completion(&xqspi->data_completion);
-		xqspi->txbuf = &opcode;
+		xqspi->txbuf = (u8 *)&op->cmd.opcode;
 		xqspi->rxbuf = NULL;
 		xqspi->tx_bytes = op->cmd.nbytes;
 		xqspi->rx_bytes = op->cmd.nbytes;
-- 
2.30.2