During writing, the entire flash page (including OOB) will be updated
with the values from the temporary buffer, so we need to fill the
untouched areas of the buffer with 0xff value to prevent accidental
data overwriting.

Signed-off-by: Mikhail Kshevetskiy <mikhail.kshevetskiy@iopsys.eu>
---
 drivers/spi/spi-airoha-snfi.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/spi/spi-airoha-snfi.c b/drivers/spi/spi-airoha-snfi.c
index 437ab6745b1a..8408aee9c06e 100644
--- a/drivers/spi/spi-airoha-snfi.c
+++ b/drivers/spi/spi-airoha-snfi.c
@@ -776,7 +776,11 @@ static ssize_t airoha_snand_dirmap_write(struct spi_mem_dirmap_desc *desc,
 		return -EOPNOTSUPP;
 	}
 
+	if (offs > 0)
+		memset(txrx_buf, 0xff, offs);
 	memcpy(txrx_buf + offs, buf, len);
+	if (bytes > offs + len)
+		memset(txrx_buf + offs + len, 0xff, bytes - offs - len);
 
 	err = airoha_snand_set_mode(as_ctrl, SPI_MODE_DMA);
 	if (err < 0)
-- 
2.51.0