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@gmail.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

1 files 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 d1d13d86b7e0..ca6369fe91ff 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. */