linux-kernel - [PATCH v2 1/2] spi: spi-mt65xx: Fix NULL pointer access in interrupt handler

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Message-ID: <20240321070942.1587146-2-fshao@chromium.org>
Date: Thu, 21 Mar 2024 15:08:57 +0800
From: Fei Shao <fshao@...omium.org>
To: Mark Brown <broonie@...nel.org>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: Fei Shao <fshao@...omium.org>,
	Daniel Kurtz <djkurtz@...omium.org>,
	Matthias Brugger <matthias.bgg@...il.com>,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-mediatek@...ts.infradead.org,
	linux-spi@...r.kernel.org
Subject: [PATCH v2 1/2] spi: spi-mt65xx: Fix NULL pointer access in interrupt handler

The TX buffer in spi_transfer can be a NULL pointer, so the interrupt
handler may end up writing to the invalid memory and cause crashes.

Add a check to trans->tx_buf before using it.

Fixes: 1ce24864bff4 ("spi: mediatek: Only do dma for 4-byte aligned buffers")
Signed-off-by: Fei Shao <fshao@...omium.org>
---

Changes in v2:
- Restore a missing curly brace being dropped during rebase
- Fix a typo in commit message (trans, not xfer)

 drivers/spi/spi-mt65xx.c | 22 ++++++++++++----------
 1 file changed, 12 insertions(+), 10 deletions(-)

diff --git a/drivers/spi/spi-mt65xx.c b/drivers/spi/spi-mt65xx.c
index 8d4633b353ee..e4cb22fe0075 100644
--- a/drivers/spi/spi-mt65xx.c
+++ b/drivers/spi/spi-mt65xx.c
@@ -788,17 +788,19 @@ static irqreturn_t mtk_spi_interrupt(int irq, void *dev_id)
 		mdata->xfer_len = min(MTK_SPI_MAX_FIFO_SIZE, len);
 		mtk_spi_setup_packet(host);
 
-		cnt = mdata->xfer_len / 4;
-		iowrite32_rep(mdata->base + SPI_TX_DATA_REG,
-				trans->tx_buf + mdata->num_xfered, cnt);
+		if (trans->tx_buf) {
+			cnt = mdata->xfer_len / 4;
+			iowrite32_rep(mdata->base + SPI_TX_DATA_REG,
+					trans->tx_buf + mdata->num_xfered, cnt);
 
-		remainder = mdata->xfer_len % 4;
-		if (remainder > 0) {
-			reg_val = 0;
-			memcpy(&reg_val,
-				trans->tx_buf + (cnt * 4) + mdata->num_xfered,
-				remainder);
-			writel(reg_val, mdata->base + SPI_TX_DATA_REG);
+			remainder = mdata->xfer_len % 4;
+			if (remainder > 0) {
+				reg_val = 0;
+				memcpy(&reg_val,
+					trans->tx_buf + (cnt * 4) + mdata->num_xfered,
+					remainder);
+				writel(reg_val, mdata->base + SPI_TX_DATA_REG);
+			}
 		}
 
 		mtk_spi_enable_transfer(host);
-- 
2.44.0.396.g6e790dbe36-goog