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>

1 files changed, 5 insertions, 4 deletions

diff --git a/drivers/mmc/host/atmel-mci.c b/drivers/mmc/host/atmel-mci.c
index 57d3cb2dbb5f..2a5d5cafeb5f 100644
--- a/drivers/mmc/host/atmel-mci.c
+++ b/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);