mmc: atmel-mci: prevent kernel oops while removing card

The removing of an SD card in certain circumstances can lead to a kernel
oops if we do not make sure that the "data" field of the host structure is
valid.  This patch adds a test in atmci_dma_cleanup() function and also
calls atmci_stop_dma() before throwing away the reference to data.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Haavard Skinnemoen <hskinnemoen@atmel.com>
Cc: <linux-mmc@vger.kernel.org>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/mmc/host/atmel-mci.c

@@ -569,9 +569,10 @@ static void atmci_dma_cleanup(struct atmel_mci *host)
 {
 	struct mmc_data			*data = host->data;
 
-	dma_unmap_sg(&host->pdev->dev, data->sg, data->sg_len,
-		     ((data->flags & MMC_DATA_WRITE)
-		      ? DMA_TO_DEVICE : DMA_FROM_DEVICE));
+	if (data)
+		dma_unmap_sg(&host->pdev->dev, data->sg, data->sg_len,
+			     ((data->flags & MMC_DATA_WRITE)
+			      ? DMA_TO_DEVICE : DMA_FROM_DEVICE));
 }
 
 static void atmci_stop_dma(struct atmel_mci *host)
@@ -1099,8 +1100,8 @@ static void atmci_command_complete(struct atmel_mci *host,
 			"command error: status=0x%08x\n", status);
 
 		if (cmd->data) {
-			host->data = NULL;
 			atmci_stop_dma(host);
+			host->data = NULL;
 			mci_writel(host, IDR, MCI_NOTBUSY
 					| MCI_TXRDY | MCI_RXRDY
 					| ATMCI_DATA_ERROR_FLAGS);