mtd: gpmi: add sanity check when mapping DMA for read_buf/write_buf

[Linux-MTD Mailing List]

Gitweb:     http://git.infradead.org/?p=mtd-2.6.git;a=commit;h=0ff76a920e3558307567b45aa0a91fb914924bfc
Commit:     0ff76a920e3558307567b45aa0a91fb914924bfc
Parent:     06f216c83c25adadc231469d51ab133afdfe110a
Author:     Huang Shijie <shijie8 at gmail.com>
AuthorDate: Wed Dec 18 23:41:00 2013 +0800
Committer:  Brian Norris <computersforpeace at gmail.com>
CommitDate: Mon Jan 27 21:55:03 2014 -0800

    mtd: gpmi: add sanity check when mapping DMA for read_buf/write_buf
    
    The buffer pointer passed from the upper layer may points to
    a buffer in the stack or a buffer allocated by vmalloc, and etc..
    
    This patch adds more sanity check to this buffer.
    After this patch, if we meet a buffer which is allocated by vmalloc or
    a buffer in the stack, we will use our own DMA buffer @data_buffer_dma
    to do the DMA operations. If the buffer is not the cases above, we will
    map it for DMA operations directly.
    
    Signed-off-by: Huang Shijie <shijie8 at gmail.com>
    Signed-off-by: Brian Norris <computersforpeace at gmail.com>
---
 drivers/mtd/nand/gpmi-nand/gpmi-nand.c | 31 +++++++++++++++++--------------
 1 file changed, 17 insertions(+), 14 deletions(-)

diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
index d1d13d8..ca6369f 100644
--- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
+++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
@@ -367,25 +367,28 @@ void prepare_data_dma(struct gpmi_nand_data *this, enum dma_data_direction dr)
 	struct scatterlist *sgl = &this->data_sgl;
 	int ret;
 
-	this->direct_dma_map_ok = true;
-
 	/* first try to map the upper buffer directly */
-	sg_init_one(sgl, this->upper_buf, this->upper_len);
-	ret = dma_map_sg(this->dev, sgl, 1, dr);
-	if (ret == 0) {
-		/* We have to use our own DMA buffer. */
-		sg_init_one(sgl, this->data_buffer_dma, PAGE_SIZE);
-
-		if (dr == DMA_TO_DEVICE)
-			memcpy(this->data_buffer_dma, this->upper_buf,
-				this->upper_len);
-
+	if (virt_addr_valid(this->upper_buf) &&
+		!object_is_on_stack(this->upper_buf)) {
+		sg_init_one(sgl, this->upper_buf, this->upper_len);
 		ret = dma_map_sg(this->dev, sgl, 1, dr);
 		if (ret == 0)
-			dev_err(this->dev, "DMA mapping failed.\n");
+			goto map_fail;
 
-		this->direct_dma_map_ok = false;
+		this->direct_dma_map_ok = true;
+		return;
 	}
+
+map_fail:
+	/* We have to use our own DMA buffer. */
+	sg_init_one(sgl, this->data_buffer_dma, this->upper_len);
+
+	if (dr == DMA_TO_DEVICE)
+		memcpy(this->data_buffer_dma, this->upper_buf, this->upper_len);
+
+	dma_map_sg(this->dev, sgl, 1, dr);
+
+	this->direct_dma_map_ok = false;
 }
 
 /* This will be called after the DMA operation is finished. */