[PATCH] mtd: gpmi: Fix NULL pointer dereference

[Fabio Estevam]

On Tue, Nov 12, 2013 at 12:47 AM, Huang Shijie <b32955 at freescale.com> wrote:
> 于 2013年11月12日 02:23, Brian Norris 写道:

> For imx23, the work flow is like this:
> [1] first check the fingerprint, if we can find it, we will return
> immediately.
> [2] if [1] failed, such as you erase all the partitions, the gpmi will call
> mx23_write_transcription_stamp() to write the fingerprint.
>
> So the @chip->buffer is not only used by the
> mx23_check_transcription_stamp(),
> but _also_ used by the mx23_write_transcription_stamp() when the gpmi
> can not find any
> fingerprint in the NAND page.
>
>
> That's why i use the NAND_OWN_BUFFERS, the buffer can be used by both
> the mx23_check_transcription_stamp()
> and mx23_write_transcription_stamp().

Understood.

What if we just allocate the 4-byte buffer once on probe?

Like this:

diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
index a9830ff..647da1b 100644
--- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
+++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.c
@@ -1342,7 +1342,6 @@ static int mx23_check_transcription_stamp(struct
gpmi_nand_data *this)
     unsigned int search_area_size_in_strides;
     unsigned int stride;
     unsigned int page;
-    uint8_t *buffer = chip->buffers->databuf;
     int saved_chip_number;
     int found_an_ncb_fingerprint = false;

@@ -1368,10 +1367,10 @@ static int
mx23_check_transcription_stamp(struct gpmi_nand_data *this)
          * and starts in the 12th byte of the page.
          */
         chip->cmdfunc(mtd, NAND_CMD_READ0, 12, page);
-        chip->read_buf(mtd, buffer, strlen(fingerprint));
+        chip->read_buf(mtd, this->buffer, strlen(fingerprint));

         /* Look for the fingerprint. */
-        if (!memcmp(buffer, fingerprint, strlen(fingerprint))) {
+        if (!memcmp(this->buffer, fingerprint, strlen(fingerprint))) {
             found_an_ncb_fingerprint = true;
             break;
         }
@@ -1401,7 +1400,6 @@ static int mx23_write_transcription_stamp(struct
gpmi_nand_data *this)
     unsigned int block;
     unsigned int stride;
     unsigned int page;
-    uint8_t      *buffer = chip->buffers->databuf;
     int saved_chip_number;
     int status;

@@ -1442,9 +1440,9 @@ static int mx23_write_transcription_stamp(struct
gpmi_nand_data *this)
     }

     /* Write the NCB fingerprint into the page buffer. */
-    memset(buffer, ~0, mtd->writesize);
+    memset(this->buffer, ~0, mtd->writesize);
     memset(chip->oob_poi, ~0, mtd->oobsize);
-    memcpy(buffer + 12, fingerprint, strlen(fingerprint));
+    memcpy(this->buffer + 12, fingerprint, strlen(fingerprint));

     /* Loop through the first search area, writing NCB fingerprints. */
     dev_dbg(dev, "Writing NCB fingerprints...\n");
@@ -1455,7 +1453,7 @@ static int mx23_write_transcription_stamp(struct
gpmi_nand_data *this)
         /* Write the first page of the current stride. */
         dev_dbg(dev, "Writing an NCB fingerprint in page 0x%x\n", page);
         chip->cmdfunc(mtd, NAND_CMD_SEQIN, 0x00, page);
-        chip->ecc.write_page_raw(mtd, chip, buffer, 0);
+        chip->ecc.write_page_raw(mtd, chip, this->buffer, 0);
         chip->cmdfunc(mtd, NAND_CMD_PAGEPROG, -1, -1);

         /* Wait for the write to finish. */
@@ -1728,6 +1726,10 @@ static int gpmi_nand_probe(struct platform_device *pdev)
         return -ENOMEM;
     }

+    this->buffer = devm_kzalloc(&pdev->dev, strlen(fingerprint), GFP_KERNEL);
+    if (!this->buffer)
+        return -ENOMEM;
+
     platform_set_drvdata(pdev, this);
     this->pdev  = pdev;
     this->dev   = &pdev->dev;
diff --git a/drivers/mtd/nand/gpmi-nand/gpmi-nand.h
b/drivers/mtd/nand/gpmi-nand/gpmi-nand.h
index a7685e3..e88114c 100644
--- a/drivers/mtd/nand/gpmi-nand/gpmi-nand.h
+++ b/drivers/mtd/nand/gpmi-nand/gpmi-nand.h
@@ -186,6 +186,7 @@ struct gpmi_nand_data {

     /* private */
     void            *private;
+    uint8_t         *buffer;
 };